1980 PhD La Trobe Univ. Melbourne, Australia 1988 Dr. med. habil. Univ. of Munich, Germany 1996 Prof. of Med. Psychology Univ. of Munich, Germany 1997 Investigador Titular "C" TC Univ. Nacional Autónoma de México 2009 Sist. Nac. Invest. nivel III Univ. Nacional Autónoma de México
Abstract: Background: The role of the endothelial cell (EC) in blood flow regulation within the central nervous system has been little studied. Here, we explored EC participation in morphological changes of the anterior hypothalamic paraventricular nucleus (PVN) microvasculature of female rats at two reproductive stages with different metabolic demand (virginity and lactation). We measured the inner capillary diameter (ICD) of 800 capillaries from either to the magnocellular or parvocellular regions. The space occupied by neural (somas, dendrites and axons) and glial, but excluding vascular elements of the neurovascular compartment was also measured in 100-â£m2 sample fields of both PVN subdivisions.
Results: The PVN of both groups of animals showed ICDs that ranged from 3 to 10 microns. The virgin group presented mostly capillaries with small ICD, whereas the lactating females exhibited a significant increment in the percentage of capillaries with larger ICD. The space occupied by the neural and glial elements of the neurovascular compartment did not show changes with lactation.
Conclusions: Our findings suggest that during lactation the microvasculature of the PVN of female rats undergoes dynamic, transitory changes in blood flow is represented by an increment in the ICD through a self-cytoplasmic volume modification reflected by EC changes. A model of this process is proposed.
Abstract: High mortality in rearing of domestic rabbits is not only an economic problem but also an animal welfare issue. Among the reasons for this high mortality are some common rearing practices. In this review, we point out several commonly used management practices, which neither represent adequate housing conditions according to the animalsâ behavioural requirements nor correspond to their nutritional needs. Sometimes, the doe has to build the nursery nest on the cage floor or in a box with a permanently open entrance, often not protected from the light. This can lead to perinatal mortality due to disturbed behaviour of the mother such as failure to build a proper nest, depositing the kits outside the nest, or infanticide. Furthermore, continuous housing of the doe with the kits does not conform to this speciesâ pattern of unusually limited maternal care. Possibly stimulated by olfactory and acoustic signals emanating from the nest, the doe can disturb the inactivity of the kits by her frequent entries to the nest or attempts to close the entrance. Cooling of the kits caused by maladaptive maternal behaviour under such conditions can also contribute to increased mortality and morbidity during the nursing period. In addition, when the doe is left to nurse the kits longer than four weeks, which does not conform to the reproductive biology of the rabbit, kit morbidity can be increased by the following factors. Although the doe's milk has a high protective role against main digestive disorders, prolonged mother-offspring contact might increase the risk of the kits becoming infected with pathogens such as coccidiosis, EPEC and pasteurellosis persisting in the doe. Pre-disposition of the kits to bacterial enteropathies can be encouraged by the delayed development of the enzymatic system, the delayed establishment of a stable gut flora, as well as by consumption of the doeâs feed. The increased energy demands of lactation as well as mastitis incidence due to prolonged suckling by the kits could decrease the fertility and the lifespan of the doe. Feed with a high content of non-fibre carbohydrates (compared to green forage) can promote bacterial enteropathies when given before the development of the kitsâ digestive functions is completed. The risk of the outbreak of such diseases is enhanced by intestinal coccidiosis and unstable gut flora. Enteropathies are also exacerbated by the use of deep litter as opposed to housing rabbits on perforated floors.
Abstract: Manganese is of growing concern as a toxic air pollutant. It is readily transported from the olfactory epithelium to the olfactory bulb, and unlike other metals, it is transported transynaptically to structures deep within the brain. However, little is known regarding the possible effect of nonoccupational exposure to manganese on olfactory function. Using the Sniffinâ Sticks test battery, we compared the olfactory performance of subjects from a manganese mining district living <1 km from a manganese processing plant, with nonexposed subjects living 50 km from the closest source of exposure (N = 30/group). Groups were matched for age, sex, and schooling, and none had ever worked in mining-related activities. Concentrations of manganese in hair were measured as a biomarker of exposure; exposed subjects had significantly higher concentrations than nonexposed subjects. They were also significantly outperformed by the nonexposed subjects on all olfactory measures (threshold, discrimination, and identification), indicating adverse effects of manganese exposure on a range of olfactory functions, including those involving higher order cognitive processes. This contrasts with previous findings showing adverse peripheral but not central effects on olfactory function of big city air pollution, which mostly consists of toxicants known to affect the olfactory epithelium but with lower transynaptic transport capacity compared with manganese. We conclude that nonoccupational exposure to airborne manganese is associated with decrements in both peripheral and central olfactory function.
Abstract: Newborn kittens and piglets show some notable similarities in suckling-associated behaviours. Both develop a pattern of teat use in which each member of the litter predominantly occupies one or two particular nipples or teats, both show agonistic behaviour towards littermates during suckling, and both are born with âweaponsââ kittens with sharp claws and piglets with sharp needle teeth. Traditionally, the differential use of nipples or teats has been thought to be due to differential quality of the mammary glands. However, neither our findings in kittens nor an examination of the literature on piglets support this view. As mammary glands usually are of equal quality and as there are normally more glands than young, there seems little reason for littermates to fight. Furthermore, there is also little evidence that individual performance in suckling contests or use of âweaponsâ is related to weight gain or to dominance relations. Given the present lack of satisfying adaptive explanations for the seemingly aggressive behaviour and use of weapons by kittens and piglets we suggest these to be epiphenomena of developmental processes anticipating the use of these behaviours and structures in later adaptive contexts.
Abstract: Suckling provides a well-defined and functionally significant context in which to study mammalian sibling competition and the possible consequences of this for long-term differences in individual behavior, physiology and life histories. There have, however, been surprisingly few studies of suckling behavior, even in species as accessible as the domestic dog. In a first approach, we filmed the suckling behavior of 10 litters (47 puppies) of various dog breeds in their ownersâ homes during the first postnatal month before the start of weaning. The pattern of nipple use was very similar across litters but very different to the better-studied pig or cat. Puppies showed only weak preference for particular (central) nipple rows, they often switched nipples during nursing sessions, and showed no evidence of teat consistency in which each littermate uses primarily one or two particular nipples. They also showed very little agonistic behavior that could be interpreted as contesting access to nipples. The present findings provide a reminder of the diversity of suckling patterns among altricial mammals and of the need for more comparative information to better understand the reasons for and functional significance of such differences.
Abstract: The altricial young of the European rabbit (Oryctolagus cuniculus) are not brooded by the mother, and although they are born into an underground nest, depend importantly on the warmth and insulation provided by littermates for their early growth and survival. Consistent with previous studies, heavier pups occupied more central, thermally advantageous positions in the litter huddle, maintained higher body temperatures, obtained more milk, were more efficient at converting it to body mass, and consequently grew faster than their lighter sibs occupying the periphery of the huddle. In the present study we measured the expression of uncoupling protein 1 (UCP-1), which is essential for the metabolism of brown adipose tissue to generate body heat in response to cold. In nine litters of domestic rabbits maintained for the first four postnatal days at temperatures below their critical thermoneutral temperature, peripheral pups showed greater expression of UCP-1 than intermediate pups, and these greater expression than central pups. This suggests that during early development littermates of the rabbit experience differing degrees of activation of the sympathetic nervous system as a consequence of exposure to different thermal environments associated with different positions in the litter huddle. Whether this is associated with long term differences in the physiological response to cold and perhaps in the manner of responding to other environmental challenges is currently under investigation.
Abstract: Information on animal reproduction is critical for the application of wildlife conservation plans. The lesser long-nosed bat (Leptonycteris yerbabuenae) is classified as threatened in Mexico; however, many aspects of its reproductive biology are still unstudied. The formation of a dorsal patch in males of Leptonycteris spp. during the mating period has been described and evidence suggests this patch is involved in reproductive behavior. We determined the male reproductive cycle of L. yerbabuenae over time based on the seminiferous cycle. We then related these internal indicators with 3 external indicatorsâtestis size, dorsal patch size, and female/male ratio in the population. Finally, we evaluated whether the epididymis functions in long-term sperm storage. Bats were captured monthly and external indicators were registered. Three adult males were euthanized each month for the evaluation of internal indicators. We determined only 1 period of spermatogenesis per year beginning in September and completing in January. The seminiferous epithelium cycle showed 11 stages and 14 steps. Internal reproductive indicators were correlated with external indicators. External testis size and female/male ratio were positively correlated with dorsal patch size. A testis size of approximately 48.2 mm2 corresponded with the beginning of sperm production. The epididymis was not involved in long-term sperm storage. This study provides the 1st description in L. yerbabuenae of the annual timing of the male reproductive cycle based on histological characteristics, and also reports a relationship between the size of the dorsal patch and male reproductive function.
Abstract: Longer-range acoustic parent-offspring communication is widespread, but might be absent in species in which young are hidden in burrows during the mother's absence. The European rabbit (Oryctolagus cuniculus) is such a species, with unusually limited maternal care largely restricted to a short daily nursing bout. Based, however, on evidence of frequent infanticide in this species, we hypothesize that rabbits possess a mechanism promoting a maternal response to pup distress calls. We conducted playback experiments with distress calls of pre-weaning pups played next to the breeding burrows of mothers in a field enclosure (i.e. next to the burrows where mothers give birth and raise their young). Calls were played shortly after pups were born (T1) when infanticide risk is maximal, and shortly before the pups start dispersing from the breeding burrow (T2). A high proportion of mothers (60.6%) responded to pup calls by rapidly returning to their breeding burrow and 40% of them investigated the area around the entrance. Return responses to the playback of pup calls did not differ between mothers during T1 and T2. Thus, our results confirm that rabbit mothers respond rapidly to pup distress calls and that this responsiveness may adaptively serve to repel potentially infanticidal females.
Abstract: The rabbit Sylvilagus cunicularius is endemic to Mexico and is one of the largest, most widespread, but little studied of the countryâs ten rabbit species. As part of a project investigating its reproductive biology, we describe here for the first time the nursery burrow, vital for the survival of the altricial young. During the breeding seasons of 2008â2012, we collected data from 25 nursery burrows and 22 nests constructed by eight females (three wild caught and five captive bred) kept in enclosures within their natural habitat in the Malinche National Park in the central Mexican state of Tlaxcala. Although not a burrow-living species, several days before parturition, females dug a nursery burrow in which they constructed a nest. These burrows were 24 short, shallow tunnels with a median length of 23 cm, typically located beneath grass tussocks or shrubs, and ending in a nest chamber a median 17 cm beneath the surface. Nests consisted of dry grass, fragments of woody plants, pine needles, and alfalfa hay and oat straw provided as supplementary food, fur pulled from the motherâs body, and her fecal pellets. Females nursed their young at the burrow entrance, and until the young were approximately 12 days old, they closed the entrance after each visit in such a way as to make it very difficult for humans to locate. Surprisingly, these nursery burrows were more similar to those of the European rabbit Oryctolagus cuniculus and the pygmy rabbit Brachylagus idahoensis than to other Sylvilagus species studied to date. As almost 50 % of burrows did not result in emergent young, present work is directed to determining what characterizes successful burrows.
Abstract: Individual consistencies over time in the behavioral responses to challenging situations are usually considered as an indication for the existence of animal personality types. Although such consistencies have been found in a variety of species, information on long-term stabilities is scanty, in particular across different life history stages such as reproductive and non-reproductive periods, which have the potential to impact considerably on the behavioral responses of animals. In our study of adult female laboratory mice, we explored the stability of behavioral responses across a 43-day period by successively testing the animals on an elevated plus maze. We tested two groups, one group that had offspring during the first two tests but not during the last test, and the other group that only had offspring during the last test situation. We found clear evidence for individual consistencies over time by means of positive significant correlations across the different test situations: Animals that spent more time in the closed arms of the plus maze and those that entered the open arms more often during the first test also tended to do so during the second test - when still in the same reproductive state, and also during the third test - when in a different reproductive state. In addition, females of the two groups did not differ overall in their responses, although we found a significant increase in the frequency and duration of presumed anxiety-related behaviors during the course of the experiment, contradicting the notion that habituation effects should attenuate the challenge of the test situation. In conclusion, our study strongly suggests the existence of stable personality types in female laboratory mice, even across different reproductive stages.
Abstract: Recent studies suggest that the main olfactory bulb (OB) represents a functional circadian pacemaker. In many altricial mammals, during preâvisual stages of development, the olfactory system plays a vital role in their survival. One remarkable example is the European rabbit; the newborns are usually maintained in a dark nursery burrow, and the lactating female briefly visits her young approximately once every 24 hours. Under these conditions, newborn rabbits depend on the circadian system to anticipate the arrival of the lactating doe as well as on pheromonal cues on the mother's ventrum to locate nipples and suckle efficiently. To investigate the development of the rabbit's circadian system, we characterized the 24âhour expression patterns of clock genes in the OB and suprachiasmatic nucleus (SCN) of preâvisual weekâold rabbits and compared these with the expression patterns in visual juvenile rabbits several weeks after weaning. We report for the first time that Per1, Cry1 and Bmal1 are expressed in the OB of newborn and juvenile rabbits. In addition, the diurnal pattern of clock gene expression develops earlier in the OB than in the SCN of newborn rabbits. Due to the early maturation of the molecular clockwork and the biological relevance of this structure during development, it is possible that the OB plays an important role in temporal regulation during preâvisual stages in rabbits.
Abstract: The European rabbit Oryctolagus cuniculus is an important model system in the study of mammalian maternal behavior. This is at least partly due to the rabbitâs unusually limited pattern of maternal care, characterized by the mother briefly visiting the young to nurse just once approximately every 24 h. In studies of domestic breeds under laboratory conditions it has been found that females show a rather predictable interval between these once-daily visits. However, as there are reports of considerable inter- individual variation, the aim of our study was to identify factors with the potential to modify the rabbitâs diurnal pattern of nursing, such as characteristics of the mother, litter size and also potential changes in the nursing interval length during the early postnatal period. We studied the time course of nursing visits in wild-type rabbits in the natural setting of a large field enclosure in order to obtain results unbiased by laboratory artifacts. Using an automatic portable gas analyzer, we monitored the timing of nursing events by recording the change in oxygen concentration within natural breeding burrows occurring when mothers entered to nurse and calculated the interval length between successive nursing events. During the first nine postpartum days, when our study was conducted, rabbit mothers on average showed a nursing interval of about 24 h. Return intervals remained rather constant in mothers of larger litters but decreased in mothers with smaller litters, resulting in them visiting their young to nurse a little earlier each night. Mothersâ age, day length and season did not affect nursing intervals. In conclusion, our study confirms that under natural conditions rabbits nurse their young only once approximately every 24 h, but that this pattern is not completely fixed and can be modulated by litter size, possibly via the strength of sucking stimulation received by the mother during nursing.
Abstract: Many aspects of an animal's early development contribute to the emergence of individual differences in physiology. Here we asked whether litter size, birth mass, suckling success and postnatal growth were predictors of individual differences in testosterone (T) and corticosterone (CORT) levels in neonatal domestic rabbits. Serum concentrations of both hormones, which we measured on postnatal day 8, were significantly and positively correlated with pup growth and milk intake. Litter size and birth mass were not significantly correlated with levels of T and CORT, although both parameters were indirectly associated with the levels of these hormones via their effects on milk intake and pup growth. Our results highlight the importance of naturally occurring features of the postnatal environment in shaping individual differences in T and CORT levels during early life.
Abstract: Interest has been growing among behavioral biologists in individual differences in animal behavior of the kind that can be considered to reflect differences in personality. Once considered the exclusive domain of human psychology, biologists have found evidence for personality across a wide range of species, while behavioral ecologist and theoretical biologists recognize the likely evolutionary origins and contribution to fitness of such. However, until recently most work has concentrated on ultimate questions of fitness and thus on adult animals, with little attention given to proximate, developmental origins. This is now changing, as approaches to studying animal personality broaden and methodologies are developed enabling this to be studied across periods of near continuous and often rapid ontogenetic change. Debate continues, however, about the right methodologies to characterize the phenomenon and then in a comparable manner across taxa that differ as widely in the expression of âpersonalityâ and insects and mammals. This makes it necessary to discuss this field in an interdisciplinary context among psychologists and biologists, and was the rational for a meeting on âThe Emergence of Personality in Animalsâ held in May 2010 at the Center for Interdisciplinary Research (Zentrum für interdiziplinäre Forschung; ZiF), Bielefeld, Germany. The diversity of topics, viewpoints and organisms covered and the excitement created by the ensuing discussions is reflected in the resulting collection of papers forming this special issue.
Abstract: This study aimed to determine whether there are regional influences on attitudes toward olfaction. A total of 1082 participants aged 21-50 years from 4 different regions (Mexican, Korean, Czech, and German) were asked to rate general attitudes toward olfaction in everyday life. To examine affective attitudes to odors (i.e., pleasantness), participants were also asked to list 3 odors as being the most pleasant or unpleasant, respectively. Next, the mentioned odor names were attributed to 1 of 4 main categories: "Food & Drink," "Social relationship," "Nature," and "Civilization" and the distribution of these categories was compared across regions. Mexicans were significantly different to the other regions in their general attitudes toward olfaction. In addition, in all regions, in comparison with men, women indicated a higher interest in the sense of smell. Moreover, a significant positive correlation was present between individuals' self-rating of olfactory sensitivity and general attitudes toward olfaction. Finally, there were significant cross-regional differences in affective attitudes toward specific categories of odors. In conclusion, our findings support and extend the notion that regions affect attitudes toward the olfactory world.
Abstract: Interest has been growing in the influence siblings may have on individual development. While mammalian research has tended to emphasize competition among siblings for essential but often limited resources such as the mother's milk, there is also evidence of mutual benefits to be had from sibling presence, most notably for altricial young in enhanced thermoregulatory efficiency. In the present study we asked whether littermates of an altricial mammal, the domestic rabbit, might gain other developmental benefits from sibling presence. From postnatal days 1 to 25 we raised rabbit pups either together with their littermates or alone except for the brief, once daily nursing characteristic of this species, while controlling for litter size and ambient nest box temperature. At weaning on Day 25 the young were then transferred to individual cages. Before weaning, we found that pups raised separately from their littermates obtained less milk, and showed lower weight gain and slower development of the ability to maintain body equilibrium than their litter-raised sibs. This was the case even though the two groups did not differ in birth weight or in the ratio of converting milk into body mass in their temperature-controlled nest boxes. Postweaning, the isolation-raised animals were also less successful in competing for food and water when tested after deprivation than their litter-raised sibs. The present study adds to the growing evidence of the influence, in this case positive, that sibs (or half sibs) may have in shaping one another's development.
Abstract: Many aspects of an animalâs early development might potentially contribute to long-term individual differences in physiology and behavior. Here we asked whether differences among littermates of the domestic rabbit in the position in the litter huddle that they occupy during the early nest period might contribute to the development of distinct behavioral and physiological phenotypes. In each of 12 litters we determined the pup occupying the most peripheral, the most central, and an intermediate position in the huddle during the first postnatal week. We then tested the responses of these same individuals as nestlings, juveniles and young adults when confronted by a range of age-appropriate environmental challenges. Two behavioral tests appeared particularly discriminatory in identifying differences associated with early position in the huddle; latency of pre-weaning pups to jump down from a shelf, and the response of young adults to the fearful screams of a conspecific. In both cases animals that had occupied the periphery of the huddle showed behavioral responses indicative of a more proactive behavioral style than their âintermediateâ or âcentralâ littermates. We conclude that while consistent long-term differences in behavioral style associated with early position in the litter huddle exist in rabbits, future work is needed to confirm the causal nature of this association, to identify underlying mechanisms, and to refine methods of behavioral and physiological testing across the life span.
Abstract: Although most mammals grow up in the company of same or different age sibs (or half sibs), surprisingly little attention has been given to how relations among them might influence the development of individual differences in morphology, physiology, and behavior. Here we review evidence from our work on domestic and wild European rabbits, and more recently on laboratory rats, mice, and domestic cats, supporting the proposition that in mammals early sibling relations contribute to the development of individual differences in these three domains and thereby to long-term behavioral differences of the kind we might consider part of an animalâs behavioral style or personality. First we report a consistent and marked negative relation between litter size and individualsâ body mass at birth and weaning, as well as marked within-litter differences in prenatal body mass and placental efficiency. We then report individual differences in preweaning behaviors associated with these morphological variables such as position occupied in the litter huddle and development of motor ability, as well as physiological differences in thermoregulation, immune parameters, and endocrine indicators of stress. Finally, we report first evidence from wild rabbits that early relations among littermates may have longterm consequences for individual differences in behavioral style.We conclude that in mammals, individual differences in early growth, physiology and behavior potentially important for the development of animal personality, are shaped to an appreciable extent by early sibling relations and that this little-researched field deserves closer attention.
Abstract: A functional immune system is important for the survival of mammalian young, particularly at weaning when they lose the immunological support provided by the mother's colostrum and milk. In altricial mammals, litter size and maternal characteristics are important components of an animal's early environment, which affect postnatal growth and development. In a study of unculled litters of Long-Evans laboratory rats (Rattus norvegicus), we asked whether such parameters are also associated with the immune status of the young shortly before weaning. On postnatal day 17, we assessed numbers of several leukocyte and lymphocyte subsets, the activity of the complement system, and immunoglobulin G (IgG) concentrations in the serum. Averaging the values of all pups per litter, we found negative correlations between litter size and lymphocyte counts, complement system activity and IgG concentration. Maternal effects were seen in the positive correlation between maternal postpartum body mass and granulocyte and monocyte counts. In addition, lymphocyte and monocyte counts as well as complement activity were lower for the young of multiparous than of primiparous mothers. This suggests a trend towards a better developed immune system in such offspring, which may be relevant for their immediate and long-term survival. The effects described here have potential implications for the design and interpretation of biomedical studies of immune parameters in laboratory rats.
Abstract: Some of the strongest evidence for sex differences in human cognition relate to spatial abilities, with men traditionally reported to outperform women. Recently, however, such differences have been shown to be task dependent. Supporting the argument that a critical factor selecting for sex differences in spatial abilities during human evolution is likely to have been the division of labor during the Pleistocene, evidence is accumulating that women excel on tasks appropriate to gathering immobile plant resources, while men excel on tasks appropriate to hunting mobile, unpredictable prey. Most research, with the exception of some recent experimental field studies, has been conducted in the laboratory, with little information available on how men and women actually forage under natural conditions. In a first study, we GPS-tracked the foraging pathways of 21 pairs of men and women from an indigenous Mexican community searching for mushrooms in a natural environment. Measures of costs, benefits and general search efficiency were analyzed and related to differences between the two sexes in foraging patterns. Although men and women collected similar quantities of mushrooms, men did so at significantly higher cost. They traveled further, to greater altitudes, and had higher mean heart rates and energy expenditure (kcal). They also collected fewer species and visited fewer collection sites. These findings are consistent with arguments in the literature that differences in spatial ability between the sexes are domain dependent, with women performing better and more readily adopting search strategies appropriate to a gathering lifestyle than men.
Abstract: An animal's environment during early life can strongly affect its physiological development. For example, litter size, i.e. the number of litter siblings, has been previously shown to strongly affect early growth in many small mammal species including laboratory rats. In the present study we tested whether natural, unmanipulated litter size is also associated with differences in stress hormone levels in young Long-Evans laboratory rats. We found a negative correlation between serum corticosterone (CORT) concentrations and litter size during two different stages of juvenile life. On postnatal day 17, shortly before weaning, this relationship was apparent with respect to basal CORT values. On day 33, however, two weeks after weaning, we found this relationship only when animals were challenged by a 10-min test on an elevated plus maze, but not in control animals (basal values). Although the physiological basis of these differences is not clear, we discuss two main, not mutually exclusive possibilities: (a) delayed maturation of the HPA axis in typically lower body mass pups of large litters, and (b) that such pups, encountering greater competition for maternal resources, adjust to this presumably more stressful developmental environment by down-regulating responsiveness of the HPA axis. In conclusion, our study provides evidence that a naturally varying feature of the developmental environment of many altricial mammals - number of littermates - may contribute to individual differences in stress-related physiology. Furthermore, it suggests the need to consider litter-size effects when investigating differences in animals' stress responses.
Abstract: Early postnatal growth in mammals can be considerably influenced by litter size and often differs among littermates in relation to birth mass. In a study of Long Evans laboratory rats we asked whether within- and between-litter differences in body mass and growth are related to behavioral development during early postnatal life. For this, we analyzed the amount of general motor activity and the display of directed, seemingly goal-oriented interactions within the litter huddle in previsual pups. During the study period from postnatal days 2 to 11, we found significant changes in pup behavior, showing a nonlinear, quadratic shape. General motor activity and, more specifically, the display of behaviors apparently directed to reaching central positions in the litter huddle increased during the first postnatal days and then decreased again. However, pups from small litters that grow more rapidly than pups from large litters, showed a faster increase in both behaviors, whereas the young from large litters reached a higher maximum. We also found striking within-litter differences in the amount of directed behavior performed by light and heavy pups, with higher levels in the former group, most probably because light pups that have a less favorable body mass-to-volume ratio and more often occupy peripheral positions in the litter huddle, make a greater effort to reach thermally favorable central positions. In conclusion, our study shows there to be consistent between-litter as well as within-litter differences in behavioral patterns during early life. These differences might have important implications for an individual's long-term behavioral and physiological performance.
Abstract: This work explores search trajectories of children attempting to find targets distributed on a playing field. This task, of ludic nature, was developed to test the effect of conspicuity and spatial distribution of targets on the searcherâs performance. The searcherâs path was recorded by a Global Positioning System (GPS) device attached to the childâs waist. Participants were not rewarded nor their performance rated. Variation in the conspicuity of the targets influenced search performance as expected; cryptic targets resulted in slower searches and longer, more tortuous paths. Extracting the main features of the paths showed that the children: (1) paid little attention to the spatial distribution and at least in the conspicuous condition approximately followed a nearest neighbor pattern of target collection, (2) were strongly influenced by the conspicuity of the targets. We implemented a simple statistical model for the search rules mimicking the childrenâs behavior at the level of individual (coarsened) steps. The model reproduced the main features of the childrenâs paths without the participation of memory or planning
Abstract: The study of human foraging behavior is relevant for social anthropology and behavioral ecology, because it makes it possible to study directly the relationship between human communities and the forest resources they use and manage. The recording of individual search pathways in the field has improved, in recent years, due to the availability of satellite technologies like the Global Positioning System (GPS). The present study was carried out in a Nahua community in Tlaxcala, Mexico, where wild fungi constitute an important source of food and income. We discuss different methods used to record foraging paths in humans as well as the spatial location of fungi gathered. Likewise, we mention the difficulties and procedures we have found useful in overcoming them. The best recordings were obtained when the GPS device was: 1) Programmed to record geographical position by time rather than distance intervals; 2) Carried by the researcher; and 3) Used to mark the sites in the forest where fungi were collected. Although the sample size explored was small, we believe that the analysis of the paths obtained using this method can provide insights into the decisions that underlie the foraging patterns of humans, as well as the possible relation between these and the spatial distribution of fungi.
Abstract: The adoption of new food resources can be facilitated by the ability to learn through observation of other individuals who use them. This behavior, termed observational learning, applies to any problem solving in which a naive individual who has observed an experienced individual learns a behavior faster than another who has not. Hummingbirds consume nectar from flowers of a large number of plant species, which are very diverse in morphology and color. During their local or migratory movements, they can observe the use of floral resources by conspecifics and heterospecifics which may change their foraging preferences. Although there is evidence that hummingbirds can use observational learning to exploit new floral resources, it is necessary to generate additional information by studying different hummingbird species. In this work, the learning performance of White-eared hummingbirds (Hylocharis leucotis) was studied in the presence or absence of a knowledgeable tutor. In a first experiment, naïve hummingbirds learned to feed on arrays of artificial flower of two colors: red (previously known resource) and yellow (novel resource), where only one color had nectar. Naive hummingbirds visited red flowers faster and more often than rewarded yellow flowers. Individuals with the best performance on each color were further trained to ensure that they only visited flowers of a specific color, and were then used as tutors in the next experiment, in which new naive hummingbirds, caged individually, were allowed to observe them foraging on the artificial arrays. These naïve individual were then exposed alone to the same array used by their tutor. Tutored hummingbirds learned to feed faster and more frequently from nectar-containing flowers of the array than naive individuals. Likewise, all tutored individuals only visited flowers of the color that had been previously visited by their tutors. This study provides experimental evidence that hummingbirds taken directly from the field can use observational learning as an efficient strategy to access new floral resources.
Abstract: Little is known about the effect of big city air pollution on olfactory function. Using everyday food-related odorants we compared the olfactory performance of residents of Mexico City, a region with high air pollution, with the performance of a control population from the Mexican state of Tlaxcala, a geographically comparable but less polluted region. Using psychophysical methodology, we compared the ability of thirty young adults from each lo- cation to detect and describe the odor of milk, of dimethyl disulfide as a common contaminant of milk, and to detect the presence of this contaminant when added to milk. The subjects from Mexico City detected and described the odorants at significantly higher concentrations than the control subjects from Tlaxcala, and they detected and negatively judged milk containing dimethyl disulfide at significantly higher concentrations of the contaminant than the Tlaxcala subjects. We conclude that the observed impairment of olfactory function caused by air pollution is relevant in every-day situations such as evaluating the quality of food before ingestion.
Abstract: The rabbit is particularly suitable for investigating the development of mammalian circadian function. Blind at birth, the pups are only visited by the mother to be nursed once every 24 h for about 3 min and so can be studied largely without maternal interference. They anticipate the mother's visit with increased behavioral arousal and with a rise in body temperature, both of which represent endogenous circadian rhythms. We now report that in newborn pups the suprachiasmatic nuclei of the hypothalamus (SCN; the main circadian pacemaker in mammals) show endogenous 24-h rhythmicity in the expression of the clock genes Per1, Per2, and Bmal1. Pups nursed from postnatal days 1 to 7 and fasted to day 9 showed the same rhythms of clock gene expression as normally nursed controls. We also report that these rhythms are entrained by nursing. Pups killed on postnatal days 3-4 showed the same rhythms in gene expression as pups in the previous experiment, whereas littermates subsequently nursed from postnatal days 4 to 7 with nursing delayed 6 h showed a corresponding shift in the diurnal pattern of clock gene expression. Consistent with this, two groups of pups implanted with telemetric thermal sensors and nursed 6 h apart had daily patterns in body temperature synchronized with the two different nursing times. We conclude that the expression of clock genes associated with the newborn rabbit's circadian system is entrained by nonphotic cues accompanying nursing, the exact nature of which now needs to be clarified.
Abstract: We studied the development of suckling behavior and weight gain in 11 litters (52 kittens) of free-ranging domestic cats until postnatal day 28 just before the start of weaning. In six of these litters, we also recorded milk intake and contests for access to nipples. Already within 12 hr of birth kittens showed a preference for posterior nipples, and by postnatal day 3 each had developed a preference for particular nipples. In fact, 86% of kittens used one particular nipple most often, and even when the mother changed the side she lay on to nurse. Contests for access to nipples occurred throughout the study period at an average rate of one to two contests per kitten per hour of nursing. Contrary to suggestions in the literature that kittens compete for more productive nipples, we found no relation between kittens' use of particular nipples and their weight gain, milk intake, or involvement in contests during suckling. We suggest that kittens' preference for posterior nipples as well as their establishment of an individual "teat order" might function to optimize the number of nipples remaining productive across lactation, and to reduce energetically costly scrambles and potentially injurious contests among littermates.
Abstract: In 60 kittens (11 litters) from free-ranging domestic cats we investigated the role of chemical cues in facilitating nipple attachment and suckling during the first month of postnatal life when kittens are totally dependent on the mother's milk. Kittens were tested both together and individually on sedated females in different reproductive states. We found (1) that newborn kittens with no suckling experience responded to the ventrum of lactating but not to the ventrum of nonlactating females with search behavior and attached to nipples within minutes; (2) that even in older kittens, nipple attachment depended on females' reproductive state, with virtually no attachments on nonreproducing females, some on pregnant females, the greatest number on early-lactating females, followed by a decline on late-lactating females; and (3) that kittens could locate their particular, most used nipple on their mother but not on a female of similar lactational age, even after eye opening. We suggest that kittens respond from birth with efficient nipple-search behavior to inborn olfactory cues on the mother's ventrum, that emission of these is under hormonal control, but that kittens also quickly learn olfactory cues specific to their own mother and to their own particular nipples.
Abstract: Surprisingly little is known about the effects of big-city air pollution on olfactory function and even less about its effects on the intranasal trigeminal system, which elicits sensations like burning, stinging, pungent, or fresh and contributes to the overall chemosensory experience. Using the Sniffin' Sticks olfactory test battery and an established test for intranasal trigeminal perception, we compared the olfactory performance and trigeminal sensitivity of residents of Mexico City, a region with high air pollution, with the performance of a control population from the Mexican state of Tlaxcala, a geographically comparable but less polluted region. We compared the ability of 30 young adults from each location to detect a rose-like odor (2-phenyl ethanol), to discriminate between different odorants, and to identify several other common odorants. The control subjects from Tlaxcala detected 2-phenyl ethanol at significantly lower concentrations than the Mexico City subjects, they could discriminate between odorants significantly better, and they performed significantly better in the test of trigeminal sensitivity. We conclude that Mexico City air pollution impairs olfactory function and intranasal trigeminal sensitivity, even in otherwise healthy young adults.
Abstract: In European rabbits, the distal urethra (DU) opens into the anterior pelvic vagina forming a single canal by which females copulate, give birth, and urinate. We investigated whether the histological characteristics of the DU and the pelvic and perineal vagina are different. The DU and vagina of rabbits (Oryctolagus cuniculus) were cut and stained with hematoxylin-eosin and Masson's trichrome (n = 3). Data were compared by using Friedman's ANOVA for repeated measures. The walls of the DU and vagina are composed of mucosa, submucosa, smooth muscle, and an external layer. Differences in tissue characteristics of the mucosa, orientation of the smooth muscle fibers, components of the external layer (connective tissue, blood vessels, and striated musculature), and thickness of the tissue layers were found among regions. The lack of histological homogeneity along the urethra and vagina possibly reflects differences in the functions of each segment.
Abstract: Interest is growing among psychobiologists and behavioral ecologists in the role of sibling relations in shaping individual development and life histories. In litters of domestic rabbits Oryctolagus cuniculus the heaviest pups at birth are more likely to survive the critical first postnatal week, they compete more effectively with littermates for milk and well-insulated positions in the litter huddle, and are the heaviest at weaning. Here we report that high birth weight pups are also better able to maintain body equilibrium. Testing pups' ability to maintain equilibrium when placed on a 15 degrees ramp for 2 min each day during the first postnatal week, we found that pups showed a continual daily improvement in their ability to maintain balance while moving on the ramp, rarely lost balance by postnatal day 8, and that heavier pups could maintain balance better and earlier than their lighter littermates. Better ability to maintain body equilibrium, however achieved, may help explain heavier pups' advantage in competing for vital resources such as milk and in gaining access to better-insulated positions in the litter huddle. It also provides further support for the usefulness of birth weight, not only as an absolute measure but also relative to the weight of other littermates, as a predictor of different developmental trajectories, behavioral and physiological, among same-age siblings in this mammal.
Abstract: Competition among mammalian siblings for scarce resources can be severe. Whereas research to date has focused on competition for the motherâs milk, the young of many (particularly altricial) species might also be expected to compete for thermally favorable positions within the nest, den, or litter huddle. We investigated this in newborn pups of the European rabbit Oryctolagus cuniculus, a species in which the altricial young are not brooded by the mother, and in which competition for milk is severe. In eight unculled litters (Nâ=â86 pups) of a domestic chinchilla strain, we calculated huddling indexes for individual pups on postnatal days 2â5 as a measure of the degree of insulation they received from littermates. Pups maintained almost constant physical contact with the litter huddle. They performed brief but frequent rooting and climbing behaviors, which usually improved their huddling index, interspersed with longer periods of quiescence during which their huddling index declined. As expected, we found a significant positive relation between pupsâ mean huddling index and body temperature. Unexpectedly, however, we did not find a relation between huddling index and pupsâ birth weight, survival, milk intake, or efficiency of converting milk to body mass. We conclude that rather than competing for thermally advantageous positions within the huddle newborn rabbits share out thermally advantageous positions as they move in a continual dynamic flow through it. Thus, in newborn rabbits, competition for the motherâs milk exists alongside mutual âcooperativeâ benefits of littermate presence.
Abstract: Many vertebrates grow up in the company of same or different-age siblings, and relations among them can be expected to significantly influence individual life histories and the development of individual morphological, physiological, and behavioral phenotypes. Although studies in birds still dominate and have stimulated most theoretical considerations, the increasing number of mammalian studies promises to broaden our understanding of this complex field by enabling interesting comparisons with the rather different bird system. It therefore seems timely to bring together recent studies of sibling relations in mammals and to demonstrate what these can offer in the way of fresh insights. In this brief review, intended to accompany a series of papers on a diverse range of mammals, we outline the current state of sibling research in mammals, comparing it to the better studied birds. Most obviously, in mammals, mother and young are in much closer contact during early life than in birds, and siblings can influence each otherâs development as well as the motherâs physiology while still in utero. During nursing, mammalian young also encounter a very different feeding situation to bird siblings. These contrasts should help stimulate further debate, as well as provide further opportunities to study the relative importance of maternal versus sibling effects on individual development. Finally, we discuss the need to balance studies of sibling competition and conflict with a consideration of the benefits accruing to individuals from sibling presence and the need for long-term studies of the influence of early sibling relations on individual development and life h
Abstract: In altricial mammals and birds, the presence of a large number of litter or brood mates often affects the development of individual offspring by reducing the share of resources provided by the parents. However, sibling presence can also be favourable, conferring thermoregulatory benefits when ambient temperatures are low. Consequently, shifts in the relation between costs and benefits of sibling presence can be expected as a function of the thermal environment. In a study of a European rabbit population (Oryctolagus cuniculus) living in a field enclosure, we investigated the effects of litter size and soil temperature on pup growth over 7 years. Temperatures inside the subterranean nests were positively correlated with soil temperature and with litter size. Soil temperature varied strongly across the breeding season, ranging from 3 to 21 degrees C. Under warmer soil temperature conditions (10-15 degrees C and >15 degrees C), pup growth decreased with increasing litter size, where litters of two pups (smallest litter size considered) showed the highest growth rates. In contrast, under colder soil temperature conditions (<10 degrees C), the highest growth rates were found in litters of three pups. We also asked if such temperature-dependent differences in the optimal pup growth rates might be explained by differences in maternal characteristics, which might affect lactational performance. We assessed maternal performance using females' postpartum body mass and social rank. However, we did not find consistent differences in maternal characteristics between females giving birth to different-sized litters during different soil temperature conditions, which would have provided an alternative explanation for the observed differences in litter size-dependent pup growth. We conclude that under colder soil temperature conditions, the thermal benefits of a greater number of littermates outweigh the negative consequences of competition for milk, leading to an environment-dependent shift in the optimal litter size for individual growth in this species.
Abstract: Birth mass can vary considerably among mammalian littermates. Heavier pups often show higher growth rates than their lighter siblings, which might positively affect fitness-relevant parameters during later life. Such a correlation between birth mass and pre-weaning growth within litters was confirmed by our study of wild-type and domestic European rabbits (Oryctolagus cuniculus) living in a semi-natural environment and under laboratory housing conditions, respectively. Our study indicates that at least two main mechanisms account for this relationship in our study species: heavier pups had a higher milk intake and also showed a more efficient conversion of milk into body mass. Furthermore, our study suggests that the better milk conversion by heavy pups was driven by three synergistic mechanisms: heavier pups had comparatively more huddling partners in the nest, they did not need to perform large amounts of proactive behavior in order to reach and remain in a central position within the litter huddle, and they could maintain a comparatively higher body temperature most probably due to their more favorable surface area to volume ratio. In conclusion, our study of European rabbits provides strong evidence that both under natural conditions and in the laboratory, within-litter differences in birth mass are maintained and may even increase during pups' early postnatal development.
Abstract: In women, birth trauma can result in altered anatomy of supporting structures of the pelvic floor and in the development of urinary incontinence. The goal of this study was to investigate the association between parturition and the morphology and function of perineal and pelvic muscles in the female rabbit. In ten nulliparous and ten multiparous same-age females, we investigated morphological, histological (n = 5 females/group), and contractile characteristics (n = 5 females/group) of the perineal bulbospongiosus (Bsm) and the pelvic pubococcygeus (Pcm) muscles. Bsm and Pcm muscles of multiparous females were significantly lighter, they had a smaller cross-sectional fiber area, and developed significantly lower twitch and tetanic tension force in response to electrical stimulation than muscles of nulliparous females. In female rabbits, multiparity is associated with potentially pathological changes in the morphological and functional characteristics of these perineal and pelvic muscles, possibly as a result of stretching during parturition.
Abstract: Effects of gonadal hormones on dimorphic striated muscles such as the bulbocavernosus/levator ani complex related to male penile erection have been widely studied. However, the action of these hormones on pelvic nondimorphic muscles is not known. In the present study, the sensitivity of the male rat pubococcygeus muscle (Pcm) to gonadal hormones was studied measuring the cross-sectional area (CSA) of its fibers. For this, two experiments were done: in the first, the effect of castration, and in the second the effect of gonadal hormone administration was analyzed. We found that castration after 6 weeks significantly reduced the average CSA of the fibers of this muscle and that castration after 2 or 6 weeks reduced the percentage of fibers with higher CSAs, but only castration after 6 weeks increased the percentage of fibers with the lowest CSA. In comparison with castrated animals implanted with an empty Silastic capsule, Silastic implants of testosterone propionate or dihydrotestosterone significantly increased the average CSA of Pcm fibers, and the treatment with testosterone propionate, estradiol benzoate, or dihydrotestosterone decreased the percentage of fibers with low CSAs and increased the percentage with larger CSAs. Our results could be considered for therapy in patients with damage of the Pcm, and suffering urinary incontinence or ejaculatory dysfunctions.
Abstract: The European rabbit, both in its wild and domesticated forms, has been a pioneer species in the study of mammalian chemical communication, and illustrates well the difficulty of understanding the functional significance of these often complex signals. Here we investigate the performance of one of the rabbit's most conspicuous chemical signaling behaviors, chin marking (chinning), and the hypothesis that this expresses social dominance. In tests of 21 chinchilla-strain sexually mature males we predicted 1) that animals would show marked and stable individual differences in the frequency of chinning, 2) that these differences would correlate with behaviors associated with dominance such as intrasexual mounting, and 3) that individual differences in the frequency of chinning and dominance-related behaviors would correlate with individual differences in a commonly used physiological indicator of dominance, concentration of serum testosterone. Supporting these predictions and consistent with previous reports, animals showed large and stable individual differences in the frequency of chinning which correlated with the behavioral indicators of dominance and less strongly, with serum testosterone. As our animals had been kept in single cages and without direct contact with other males since weaning, these findings raise the question as to how and when during development such differences among individuals arise. We are currently investigating the possible relation between pups' intrauterine position, postnatal competition among littermates for milk and thermally advantageous positions in the litter huddle, and later differences in indicators of dominance such as those reported here.
Abstract: Growth during an animal's early ontogeny can have important consequences for its health, reproduction and survival during later life. We studied pre-weaning growth rates of two species of small altricial mammals, and assessed the impact and compared the importance of two main aspects of the animals' early environment: maternal characteristics and the number of litter siblings (i.e. litter size). Study animals were wild-type European rabbits living in a field enclosure and laboratory rats kept under standardized housing conditions. Growth of rabbit pups was best explained (to 47%) by the combined effects of litter size, maternal age and whether females had given birth to another litter shortly before. Similarly, growth in rat pups was best explained (to 75%) by the combined effects of litter size, maternal body mass and whether mothers had previously given birth. In both species, litter size correlated negatively with pup growth. In rabbits, growth was greatest in litters of middle-aged females. In rats, pup growth correlated positively with maternal mass. Pups of both species showed higher growth rates when the mother had not given birth to a previous litter. Despite major differences in maternal behaviour and study conditions between the two species, the findings point to a similar ranking in the importance of the different parameters tested: Litter size, i.e. sibling number, was the most important factor, followed by maternal mass or age, and then by mothers' history of previous reproductive activity. We therefore think it likely that these findings will be valid for other mammalian species giving birth to large litters of altricial young.
Abstract: In the European rabbit (Oryctolagus cuniculus) nursing acts as a strong non-photic synchronizer of circadian rhythmicity in the newborn young. Rabbits only nurse for a few minutes once every 24 h and previous studies have shown that the pups, blind at birth, display endogenous circadian rhythms in behavior and physiology entrained by this regular daily event. As a further step toward understanding the neural organization of the rabbit's early circadian system, we investigated the expression of clock genes in the suprachiasmatic nucleus of the hypothalamus (SCN; the principal circadian pacemaker in adult mammals) across the pups' 24-h day. We used 43 pups from seven litters maintained in constant darkness and entrained non-photically by nursing at the same time each day until P7. After nursing on day 7, pups were killed in the dark at 3-h intervals so as to obtain eight groups (n=5-6 pups/group) distributed evenly across the 24 h before the next scheduled nursing. Profiles in the expression of the clock genes Per1, Per2, Cry1 and Bmal1 were determined using in situ hybridization in brain sections through the hypothalamus at the level of the SCN. We report for the first time: 1) that Per1, Per2, Cry1 and Bmal1 are all expressed in the SCN of the newborn rabbit, 2) that the expression of Per1, Per2 and Bmal1 but not Cry1 shows diurnal rhythmicity similar to that in adult mammals, and 3) that the expression of Per1, Per2 and Bmal1 is consistent with the strong entraining effect of nursing found in previous studies. Unexpectedly, and contrasting somewhat to the pattern in the SCN, we also found diurnal rhythmicity in the expression of Cry1 and Bmal1 but not of Per1 in the anterior ventromedial hypothalamic nucleus. Overall, our findings suggest that the SCN is a functional part of the newborn rabbit's circadian system and that it can be entrained by non-photic cues associated with the mother's daily nursing visit.
Abstract: Mexico has the largest number of leporid species in the world but most have been little studied. The endemic Mexican cottontailSylvilagus cunicularius (Waterhouse, 1848) is the largest Mexican rabbit, and although not in danger of extinction, it is increasingly threatened. Since little is known about its annual pattern of reproduction, we studied this species in La Malinche National Park, central Mexico, whereS. cunicularius is still common. For 7 years we trapped and marked 157 different individuals (plus 59, sometimes multiple, re-captures), determining across the year the percent of adult females that were reproductively active, the number of juveniles as a percent of total captures, and the percent of males with scrotal testes. Reproductively active females were present throughout the year but with a notable peak from March to October, juveniles were present throughout the year but with a peak from September to December, and adult males had scrotal testes throughout the year with no seasonal change in testis length. Onset of the breeding season coincided with increasing day length and temperature, and births with high rainfall. Thus, in central MexicoS. cunicularius breeds throughout the year but particularly during the warmer, wetter summer months. We therefore recommend that hunting only be permitted from November to February.
Abstract: Olfactory function is affected in different neurodegenerative diseases. Recently, it has been found that some hereditary ataxias are also associated with significant olfactory impairment. However, the initial findings did not examine the nature of the olfactory impairment associated with these ataxias. In the present article the effect of spinocerebellar ataxia type 2 (SCA2) on olfactory function was studied in 53 SCA2 patients and 53 healthy control subjects from HolguÃn, Cuba. Several tests were applied to evaluate olfactory threshold, description, identification and discrimination. The results show significant impairment in SCA2 patients on all olfactory measurements, and the pattern of olfactory deficits found suggests that they have much in common with those reported for other neurodegenerative diseases such as Parkinson's and Alzheimer's diseases.
Abstract: To our knowledge there has been no study of the effect of everyday air pollution on olfactory function. It was therefore the aim of this study to compare the olfactory performance of long-term residents of Mexico City, an environment with high air pollution, with the olfactory performance of residents of the Mexican state of Tlaxcala, a region geographically similar to Mexico City but with low air pollution. Healthy volunteers [82 Mexico City subjects (MEX), 86 Tlaxcala subjects (TLX)] 20-63 years of age and balanced for age and gender between the two localities were tested for the perception of the odors of everyday beverages presented in squeeze bottles. When tested with ascending concentrations of stimuli in a three-way oddball paradigm, residents of Tlaxcala detected the odors of instant coffee and of an orange drink at significantly lower concentrations than residents of Mexico City. They also performed significantly better in discriminating between the two similar-smelling Mexican beverages horchata and atole in an oddball test. Significant differences between the two populations in overall olfactory performance were apparent in three of the four age classes (20- to 29-, 30- to 39-, and 40- to 49-year-old subjects) but not in the 50-63 years age class. About 10% of MEX subjects compared to about 2% of TLX subjects were judged to have poor olfactory function; all were from the older age classes (mean age: 48.6 years). Thus, air pollution in Mexico City appears to have a substantial impact on olfactory function even in young and middle-aged residents.
Abstract: Retrograde labeling with horseradish peroxidase conjugated to wheat germ agglutinin showed that the pubococcygeus muscles of the female rat are innervated by a population of motoneurons located in a column approximately 2 mm in length in the central region of lamina IX of the sixth lumbar-first sacral spinal cord segments. These neurons have a dendritic distribution that projects to the lateral, medial and ventral regions of the gray matter. Values for soma size, primary dendrite length and arborization area obtained from intact animals that were in diestrous-2, were significantly reduced following ovariectomy. After hormone priming of the ovariectomized animals with estradiol benzoate and progesterone, an additional injection of estradiol benzoate alone or followed by progesterone increased the labeled length of the primary dendrites distributed to the lateral, but not to the medial or ventral regions of the gray matter in the spinal cord. However, dendritic labeling was not significantly increased when only progesterone was additionally injected. It therefore seems that pubococcygeus muscle motoneurons of the female rat are sensitive to the effects of gonadal hormones.
Abstract: When approached by males, females of the Amarillo fish (Girardinichthys multiradiatus) perform a behaviour called vibration or they are aggressively challenged. We quantified vibration and assessed whether it compromises the rate of feeding attempts in dyads kept in outdoor enclosures. Male approaches resulted in female vibration and in a reduced feeding rate. Vibration was not evoked by femaleâfemale aggression, which was frequent and always ended in the subordinate fleeing from the dominant female. Using a closed respirometer we found that vibration is costly; oxygen consumption of females was greater in the presence of a male (which evoked vibration) than in the presence of a non-familiar female (when no vibration occurred). By recording interactions of females confined in aquaria in the presence and in the absence of males, we confirmed that escaping is the only available response to deal with female aggression. Females kept without males participated in frequent aggressive (even lethal) interactions that did not abate while the subordinate female was in sight of the dominant, and which caused premature births and injuries. Yet in the alternative treatment aggression ceased when a male approached, prompting vibration in both females. Thus, in the Amarillo, in as much as it evokes energetically costly female vibrations, male courtship is an expression of sexual conflict. However, in the absence of males, frequent female aggression potentially annuls the benefits of not vibrating. We propose that a complete appraisal of the consequences of sexual conflict must include an assessment of the costs imposed by intra-sexual interactions.
Abstract: Mexico has eight endemic lagomorph species, several of which are endangered. For conservation reasons it is necessary to know more about their diet. In a first step we applied the method of fecal pellet analysis to the cottontail Sylvilagus floridanus (Allen, 1890). Since it is common in Mexico, information on its diet should provide a useful baseline with which to compare the diets of other Mexican lagomorphs. At Ixtacuixtla, we recorded vegetation and analyzed fecal pellet content once in August (wet season) and once in March (dry season) at 4 sampling sites representing different habitat types. The comparison of vegetation and diet records suggested S. floridanus to occupy the same dietary niche in the different habitats. Measures of niche breadth showed S. floridanus to be neither a generalist nor a specialist. Nevertheless, it appeared to be quite selective in consuming particular herb and grass species even when they became scarce during the dry season. Since the vegetation record only poorly represented the rabbitsâ diet, a more focused approach is suggested for future studies: first, to identify the relevant food species in the diet, second, to obtain data on the availability of these, and third, to concentrate on time points when changes in resource state could be a limiting factor.
Abstract: Rabbit pups are only nursed for about 3 min once a day. They depend on a pheromone on the mother's ventrum to locate nipples and on tactile stimulation of the muzzle to grasp them. In a continuing study of the sensory input guiding suckling behavior we investigated the whisker array in newborn pups and the possible contribution of the whiskers to suckling. Rabbits are born with approximately 76 whiskers arranged in seven to nine rows and increasing in length from rostral to caudal. No significant difference was found between pups with whiskers cut and intact controls in latency to perform the stereotyped nipple-search behavior, latency to attach to nipples, time spent on nipples, milk ingested, or in the strength of conditioning to a novel odor paired with suckling. Thus, the whiskers do not seem important for suckling in newborn rabbits.
Abstract: A notable and phylogenetically conserved characteristic of organisms is the demonstration of endogenous 24-h (circadian) rhythms across a wide range of behavioral, physiological and molecular processes. The extensive efforts to understand how such rhythms are generated and sustained have focused on their coupling to the daily light â dark cycle, that is, on their entrainment by photic cues. Although understandable given that this is the most predictable environmental information, it is increasingly clear that recurrent, non-photic events such as the periodic availability of food also regulate circadian systems and via mechanisms different to photic cues. One of the challenges facing circadian rhythms research is to understand how organisms respond to the wealth of diurnally fluctuating information around them and integrate this to generate a coherent and adaptive system of circadian function. Here we briefly review what is known about the influence of non-photic stimuli on the circadian system. We then consider the value but inherent difficulties of a developmental approach. After considering the advantages offered by the neonatal rabbit, we close by emphasizing the importance of developing models more closely tied to the animalâs natural, evolved lifestyle if sense is to be made of the diversity of information rapidly accumulating on circadian processes.
Abstract: Rabbit pups, Oryctolagus cuniculus, are nursed only for about 3 min once every 24 h, and we have previously reported indirect evidence of strong competition among littermates for the mother's milk. In the present study, we examined the nature of this competition more closely. In experiment 1, we investigated the temporal pattern of milk intake during nursing and found that pups obtain almost all milk available to them each day during the second minute of a 3-min nursing event. In experiment 2, we investigated the availability of milk across the eight nipples and found a tendency for more milk to be available from the two middle pairs. In experiment 3, we observed the behaviour of pups beneath the mother during nursing and found no evidence of a fixed âteat order,â of overt aggression, or of pups displacing one another from nipples. However, the results confirmed previous findings of a positive correlation between milk intake and pups' birth weight. In experiment 4, the attempt to increase competition among pups by covering half of the mother's nipples did not lead to the expression of overtly aggressive behaviour or to recognizable displacements from nipples. We conclude that in the rabbit, littermates compete for milk by scramble rather than by contest competition, in which the heaviest pups have a clear advantage. It is a strategy presumably well suited to a situation in which milk is effectively available only for 1 min every 24 h, leaving little time for aggressive tussles.
Abstract: In this report we argue that to understand how odors influence physiology and behavior it is necessary to understand how experience, leaning and memory shape the way they are perceived. By analyzing images and associations in response to everyday odor stimuli we found that odors are more precisely represented than is usually supposed by naming ability alone; we found positive correlations between subjects familiarity with particular everyday odors and their ability to discriminate among them; in cross-cultural studies we found ratings of intensity, pleasantness and edibility of odors by Japanese, German and Mexican subjects to be greater for familiar, culture-typical odorants than for unfamiliar, culture-atypical odorants; and in an additional study we found that the goodness of fit between subjectsâ expectation of how odorants would smell and the veridical name provided by the experimenter correlated positively with stimulus intensity and pleasantness. We also report results of studies of newborn rabbits showing that they can learn, even prenatally, odors associated with their mothersâ diet, that such learning is long-lived, and that it is associated with enhanced, odor-specific sensitivity of the olfactory epithelium. We conclude that by giving more attention to individual experience and to biological relevance of test stimuli we will find that olfaction plays a more significant role in shaping our behavior and physiology than is often supposed.
Abstract: Here we describe the nerves innervating the perineal skin together with their sensory fields in the adult female rat. Electrophysiological recording showed that the lumbosacral and L6-S1 trunks, in part by way of the sacral plexus, transmit sensory information from the perineal skin via four nerves: the viscerocutaneous branch of the pelvic nerve innervating the skin at the midline between the vaginal opening and anus, the sensory branch of the pudendal nerve innervating the clitoral sheath, the distal perineal branch of the pudendal nerve innervating a broad area of skin adjacent to the vaginal opening and anus, and the proximal perineal branch of the sacral plexus innervating a broad area of skin adjacent to the clitoris and vaginal opening. The sensory fields of three of these nerves overlapped to some degree: the viscerocutaneous branch of the pelvic and the distal perineal branch of the pudendal nerves at the midline skin between the vaginal opening and the anus, and the distal perineal branch of the pudendal nerve and the proximal perineal branch of the sacral plexus at the skin lateral to the vaginal opening. Such overlap might provide a safeguard helping to ensure that somatosensory input from the perineal region important for triggering reproductive and nonreproductive reflexes reaches the CNS.
Abstract: We present findings suggesting that photoperiod is important in determining the sensitivity of the late-pregnant rabbit uterus to oxytocin (OT). Longitudinal myometrial strips were taken from term-pregnant and estrous rabbits and mounted in an organ bath for isometric myographic recording at different times during a 16:8-h light-dark cycle (lights on 0600-2200; n = 5/group), and the strength of contractions was registered in response to the application of OT or KCl. Strength of contractions was dose dependent and was up to 200 times greater at doses three to four orders of magnitude lower in tissue taken from pregnant animals during the light phase (0700 and 1300) than during the dark phase (2400 and 0400). Strips from nonpregnant estrous females also showed greater sensitivity and contractile force when taken in the light (0700) than in the dark (0400), although the differences were not significant. Consistent with the influence of photoperiod on uterine sensitivity to OT, strips taken from two groups of pregnant females (n = 5/group) maintained on a light-dark cycle advanced 12 h showed significantly greater sensitivity and force in response to OT during the new subjective light than during the new subjective dark phase. The photoperiod-dependent contractile response to OT was specific and not simply the result of a change in general mechanical properties of the muscle, because administration of KCl resulted in dose-dependent contractions of similar magnitude in both the light and dark phase. These results are consistent with the fact that rabbits, like other nocturnal mammals, typically give birth during the day.
Abstract: Rabbits (Oryctolagus cuniculus), like many small mammals, have a marked postpartum estrus, and during the breeding season, are often both pregnant and lactating. We examined reproductive performance and allocation of resources by rabbit mothers with overlapping litters under presumably optimal conditions of unrestricted food, standardized litter size, and young reproductive age. Even under these conditions, females raising overlapping litters incurred higher costs in terms of greatly increased food intake and pup mortality than females raising nonoverlapping litters. Despite such costs, females with overlapping litters raised a larger total number of young to weaning than females without the load of simultaneous lactation and pregnancy. By more than doubling food intake during lactation, females maintained a stable baseline body weight throughout the study, suggesting that this, in a species with low fat reserves, might have priority over the short-term raising of a maximum number of young. Contrary to the expectation that females with overlapping litters would allocate more resources to their senior young, no appreciable difference in number, growth, or survival between pups of senior and junior litters was found either at birth or weaning. While this might reflect a strategy in this opportunistic breeder of distributing reproductive chances similarly between senior and junior litters, it is now necessary to investigate females' breeding strategy when resources are limited.
Abstract: There has been considerable controversy concerning the effect of hormones on the nasal epithelium and, in particular, their association with the female reproductive state.
Abstract: Newborn rabbits compete vigorously for the mother's milk, and survivors benefit from littermate deaths. Here we report that rabbit pups also may benefit from littermate presence in terms of increased thermal efficiency. Pups nursed normally once a day by their mother but otherwise raised alone had a lower probability of survival, lower body temperature, and lower efficiency of converting milk into body mass than their siblings raised with littermates. The contribution of a more favorable thermal environment to the better growth and survival of group-raised pups was supported by the finding that single pups raised at higher ambient temperatures grew more rapidly than single pups raised at lower temperatures. These effects were most clearly seen across Days 2 to 5, after which time differences between treatment groups were no longer significant. Thus, the results of this study suggest that the benefits as well as costs of having siblings must be weighed against each other when considering the manner in which sibling presence influences individual development and survival.
Abstract: We investigated whether olfactory detection threshold is correlated with phase of the menstrual cycle. Three hundred and thirty-two women 13-49 years old were tested once during either the follicular, ovulatory, luteal or menstrual phase, and 15 women 20-43 years old were tested at each of these phases across one complete cycle. In three non-cycling control groups subjects were each tested once; 83 post-menopausal women 47-86 years old, 60 pre-pubertal girls 5-12 years old, and 183 men 17-30 years old. Odor detection thresholds were determined using sniff bottles containing -log9.5 to -log6.0 concentrations of amyl acetate presented in ascending order. Thresholds differed significantly across the cycle and were lowest during the ovulatory and highest during the menstrual phase. Thresholds for all control groups were higher than for the cycling women during the ovulatory phase. The results confirm that olfactory threshold is related to phase of the menstrual cycle and thus possibly to hormonal state.
Abstract: Newborn rabbits, like other altricial mammals, demonstrate thermotaxis and when placed on a thermal gradient locate and come to rest at physiologically appropriate temperatures. Little is known, however, about the sensory-motor components contributing to the in energetic terms important decision of the young to cease locomotion and come to rest. We investigated the behavior of newborn rabbits on two thermal gradients; linear in which pups could use tactile cues from the arena wall, and concentric in which pups were unable to use such cues. On both gradients pups located the warm, thermal-neutral area within the 200-s test time, thereby demonstrating their ability to orient appropriately using thermal cues alone. Unexpectedly, however, pups on the concentric gradient failed, or took significantly longer, to come to rest than pups on the linear gradient. Since the speed of locomotion of pups on the linear gradient was significantly slowed when they were in contact with the arena wall, and in most cases they came to rest in contact with it, we suggest that not only thermal but also tactile cues may be important in bringing young mammals to rest in a thermally appropriate environment.
Abstract: Newborn rabbits are only nursed once a day for 3 to 4 min and are completely dependent on a pheromone on the mother's ventrum for the release of nipple-search behavior and sucking. However, if the mother's ventrum is perfumed, pups can be conditioned in just one 3-min nursing session to respond with nipple searching to the novel odorant. To define more precisely the reinforcing properties of the nursing situation supporting such rapid learning, odor conditioning was conducted in independent groups of 2-day-old pups after successively eliminating potential reinforcing stimuli such as the doe's behavior, milk ingestion, nipple-search behavior, or sucking nipples. All experimental groups showed significant conditioning compared to control groups subjected to similar treatments on unscented does, with the strength of conditioning indicating that behavior of the doe, milk consumption, or arousal during performance of the search behavior were not major reinforcers, but rather the opportunity to suck nipples. Thus, this study suggests intraoral stimulation associated with sucking to be an important reinforcer in this paradigm, as for early olfactory learning in other young mammals.
Abstract: Anatomical descriptions of the genitofemoral nerve (GFn) innervating the lower pelvic area are contradictory. Here we re-examine its origin and innervation by its various branches of principal target organs in the male rat. Using gross dissection, electrophysiological techniques and retrograde tracing of motoneurones with horseradish peroxidase, we confirm that the GFn originates from lumbar spinal nerves 1 and 2, and that at the level of the common iliac artery it divides into a lateral femoral and a medial genital branch. In contrast to previous studies, we report that the genital and not the femoral branch innervates the abdominal-inguinal skin, and not only the genital but also the femoral branch innervates the cremaster muscle (Cm) surrounding the testes. Motoneurones innervating the Cm proper are located in the ventral nucleus of L1 and L2, and those innervating the muscular transition region of the rostral Cm are located in the ventral nucleus in L1 and the ventrolateral nucleus in L2. The GFn may contribute to male reproductive performance by transmitting cutaneous information during copulation and, via contraction of the Cm to promote ejaculation, the protective displacement of the testes into the abdominal cavity during fighting and as a sperm-protecting thermoregulatory measure.
Abstract: This study investigates the role of prenatal odor learning on postnatal adaptive orientation responses in the newborn rabbit. Preference tests revealed that pups are equally attracted to the odors of placentae and colostrum (Experiments 1-4), suggesting that an odor continuity may exist between the fetal and neonatal environments. To test some predictions derived from this hypothesis, we manipulated the odor of the diet of pregnant-lactating does to control the chemical niches of their perinates. Fetuses exposed in this way to the odor of cumin (C) were selectively attracted as neonates to the odor of pure C (Experiment 6). Prenatal exposure to C also was followed, to a certain extent, by enhanced attraction to C odor in the placenta or colostrum from females which had consumed it (Experiments 5 & 7). Finally, the functional implications of perinatal odor continuity were tested by disrupting it. The odor component of the feto-neonatal transitional environment revealed indeed to affect the ability of certain pups to gain colostrum and milk at the very first sucking opportunities (Experiment 8).
Abstract: Little information is available on the participation of the perineal striated muscles in female reproductive processes. Here, we describe the gross anatomy and innervation of two striated perineal muscles in the female rabbit, the bulbospongiosus (BSM) and ischiocavernosus (ISM), and analyze their reflex electromyographic (EMG) activity in response to stimulation of the perigenital skin and vaginal tract. Twenty-four mature chinchilla-breed rabbit does were used: 12 to describe the anatomy and innervation of the muscles, 9 to determine reflex EMG activity of the muscles in response to stimulation of the perigenital skin and specific levels of the vaginal tract and 3 to analyze the effect of contraction of the muscles on intravaginal pressure. Both muscles were well developed, with their fibers originating at the ischiadic arch and inserting onto the ligamentum suspensorium clitoridis. Branches of the clitoral and perineal nerves innervated the BSM and ISM, respectively. Bilateral electrical stimulation of these nerves provoked retraction of the clitoral sheath and an increase in intravaginal pressure at the level of the perineal vagina. Whereas neither muscle responded to stimulation of the perigenital skin, both were reflexively activated during mechanical stimulation of the inner walls of the perineal vagina. Prolonged cervical stimulation inhibited this reflex. Thus, in reproductive processes such as copulation and/or parturition, the contraction of these muscles may be induced during stimulation of the perineal vagina.
Abstract: Three main concerns underlie this review: 1) The need to draw together the widely dispersed information available on the circadian biology of the rabbit. Although the rabbit is a classic laboratory mammal, this extensive body of information is often overlooked by chronobiologists, and despite several advantages of this species. In terms of its general biology the rabbit is the best studied laboratory mammal in the wild, it demonstrates a wide variety of robust circadian functions, and being a lagomorph, it provides a useful comparison with more commonly studied rodent species. 2) The need to more fully exploit a developmental approach to understanding circadian function, and the particular suitability of the rabbit for this. Female rabbits only visit their altricial young for a few minutes once every 24 h to nurse, and survival of the young depends on the tight circadian-controlled synchronization in behavior and physiology of the two parties. Patterns of circadian rhythmicity in neonatal pups associated with nursing do not form a smooth continuum into weaning and adult life, and may reflect the action of separate mechanisms operating in their own right. 3) Using information from the first two points, to emphasize the diversity and complexity of circadian rhythms underlying behavioral and physiological functions in adult and developing mammals. Information accruing on circadian functions in the rabbit makes it increasingly difficult to account for these in terms of one or two regulatory mechanisms or "oscillators." Thus, it is argued that in addition to the reductionist, molecular approaches currently dominating much of chronobiology, the study of circadian systems as emergent characteristics of whole organisms operating in complex environments merits special attention.
Abstract: Odor perception, including intensity, is affected by knowledge of odor source. For 76 subjects tested with 24 everyday odorants, ratings of intensity, pleasantness and familiarity were enhanced when subjects either could identify the odor source themselves or were provided with the name by the experimenter. Ratings were highest when subjects judged that the names provided matched their own perception, suggesting an interaction between individuals' cognitive representation of odors and their immediate perceptual experience.
Abstract: This study was aimed at characterising the impact of immediate postnatal sucking on pup survival and development. The interactive effects of postnatal success with the day 0 weight of pups, the nest-access regimen (controlled or free) or parity of females was investigated. Pups (n = 900) were categorised according to their initial ingestion of colostrum. In primiparous does: (1) pup mortality between d0-d10 was higher for unsuccessful than for successful early suckers; (2) lighter d0-weight reduced survival for unsuccessful but not for successful pups; (3) free nest-access of females annihilated the survival advantage fostered by the initial sucking success. In secondiparous does, these impacts waned. Finally, whatever the does' parity, only d0-weight influenced pup weight-gain between d0-21. Thus, pup survival seemed to depend (at least in primiparae) on their ability to suck right after birth, and to display a pattern of energy saving without being disturbed by the females' nest entries.
Abstract: In the wild rabbit, Oryctolagus cuniculus, motherâyoung relationships are based on restricted, once-per-day nursing interactions. Correspondingly, pups have evolved an efficient strategy of energy saving. Here we investigate under breeding conditions, whether matching or not, the once-daily nursing visit by the rabbit females has an effect on pup survival and growth. Two nursing regimen were applied to 89 primiparous (P) and to 78 multiparous (M) does: (a) one that matched the once daily nursing pattern (closed nest-box during the whole day except for a few minutes devoted to nursing) and (b) one that did not match it (24 h free nest access). In P females, the controlled nest access resulted in lower mortality between birth and weaning (8.1%) as compared to the free nest-access (18%). This effect was recorded from postnatal d 3â4 onwards. Both treatments induced different death causes (starvation (63%) in controlled-access regimen, and wounds and nest-soiling (29%) in free-access regimen). While both experimental nest-access regimens differentially affected pup survival in P or M females, they were without influence on pup growth rate in does of either parity. It is concluded that repeated nest visits by the female increase risks of injury to pups, and of out-of-time pup activation or sucking, and that, more generally, it plays against the ethophysiologigal strategy of biomass conservation evolved by rabbit newborns. The fact that the nest-access regimen no longer affected pup survival from the second parity suggests that the behaviour of multiparous does more adequately models the offspring demands.
Abstract: Transient expression of axon collaterals plays an important role in enabling neurons to find appropriate targets during development. In the olfactory bulb, the numbers of both sensory neurons and their targets, the glomeruli, increase markedly during the postnatal period. In the present study, the morphology of developing olfactory axons in the olfactory bulb of 1-21-day-old rabbits was analyzed using stereological methods and the rapid Golgi technique. The findings demonstrated a change in axon morphology from the olfactory nerve layer to the glomeruli suggestive of a sequence in axon development. In the olfactory nerve layer, axons typically had knob-like growth cones and a few collateral branches. Close to glomeruli, axons increased in thickness, formed rather complex and irregular growth cones, and typically gave off many collaterals. Within glomeruli, the axons formed terminal branches and boutons. Extraglomerular branches were apparently removed once axons had entered a glomerulus, insofar as these branches often displayed morphological signs of degeneration. In contrast, collateral branches ending in the same glomerulus remained, indicating that formation of collaterals may assist olfactory axons in locating glomerular targets.
Abstract: We sought evidence for postnatal resource limitation among littermates of the domestic rabbit Oryctolagus cuniculus, and asked whether deaths of indi~vidual pups benefit survivors by increasing their share of milk. Milk ingestion, growth and mortality of 10 chinchilla-breed captive litters were recorded between birth and age 21 d. That milk limits growth and survival was indicated by larger litters showing lower weight gain and higher mortality, and by a significant positive correlation between milk ingested by individual pups and weight increase. Within litters, pups with higher birth weights grew faster, and weight hierarchies became increasingly stable over the 3 weeks, suggesting that advantages accrued during gestation were progressively consolidated during lactation. After individual pups died, the total daily milk weight obtained by the litter was generally unaffected but per capita milk consumption and growth of surviving pups increased, and increases in per capita consumption were greater in smaller litters. The most successful competitors for milk apparently benefit from the deaths of their littermates by obtaining an increased share of an undiminished daily food supply. This relationship has not previously been demonstrated in any vertebrate.
Abstract: The gustatory responsiveness of four adult spider monkeys to five food-associated acids was assessed in two-bottle preference tests of brief duration (3 min). The animals were given the choice between a 30 mM sucrose solution and defined concentrations of citric acid, ascorbic acid, malic acid, acetic acid, or tannic acid dissolved in a 30 mM sucrose solution. With this procedure,Ateles geoffroyi was found to significantly discriminate concentrations as low as 5 mM ascorbic acid, citric acid, and acetic acid, 10 mM malic acid, and 0.1 mM tannic acid from the alternative stimulus. With the latter two substances, the monkeys rejected all suprathreshold concentrations tested, whereas with the former three substances, the animals showed an inverted U-shaped function of preference, i.e. they rejected high concentrations, but significantly preferred low but detectable concentrations of these acidic tastants over the alternative sweet stimulus. The results showed (1) the spider monkey to respond to the same range of acid concentrations as other nonhuman primate species; (2) thatAteles geoffroyi, is able to detect food-associated acids at concentrations well below those present in most fruits; and (3) that unlike most other primate species tested so far, spider monkeys do not generally reject acidic tastants but show a substanceand concentration-dependent change in responsiveness that may range from rejection to preference. The results support the assumptions that spider monkeys may use sourness and/or astringency of food-associated acids as a criterion for food selection, and that the gustatory responsiveness ofAteles geoffroyi to acidic tastants might reflect an evolutionary adaptation to frugivory.
Abstract: Young rabbits (Oryctolagus cuniculus) are only nursed for 3-5 min every 24 h. They show a circadian increase in activity in anticipation of this, which is entrained by suckling. Our aim was to determine whether serum and liver metabolites show diurnal fluctuations which could act to regulate this circadian pattern. Stomach weight, liver glycogen and serum metabolites were measured every 3 h in 7- to 8-day-old pups when normally nursed (up to 24 h after suckling) and fasted (up to 48 h after suckling). The results suggest: 1. Energy balance between feeds was maintained by a cascade in the use of fuels, first glucose from the milk, then glycogen stores and gluconeogenesis from circulating products of proteins and triglycerides, and finally, in late-fasted animals, the mobilization of free fatty acids. 2. The empty stomach and depletion of glycogen 23-24 h after the last feed could act to trigger anticipatory arousal in normally nursed pups, and the release of free fatty acids 45 48 h after the last feed could trigger this in fasted pups. 3. Unmasking of rhythmicity by fasting in serum levels of glucose and proteins suggests their regulation by endogenous oscillators, which may also be the case for the mobilization of free fatty acids.
Abstract: In any mammalian species a proper understanding of the natural, co-evolved mother-young system is of major importance if productivity is to be optimized under conditions compatible with the animal's welfare. The European rabbit (Oryctolagus cuniculus) is particularly interesting in this regard given its unusually limited and stereotyped pattern of maternal care and the equally stereotyped set of corresponding specializations in the young. For each of five key topics - the nest, parturition, nursing, suckling, and weaning - the behavior of the mother and then of the pups is described, followed by a consideration of the possible application of this information to improving husbandry.
Abstract: The olfactory system is faced with a particular problem--the high dimensionality and inherent unpredictability of the chemical world. Most natural odorants encountered in everyday life are complex mixtures of many different volatiles. This means that from the outset the olfactory system has to contend with a great and often unpredictable diversity of molecules, making it difficult for stable primary features of the chemical world to be mapped onto the sensory surface. One solution to such unpredictability is provided by learning. Learning confers flexibility, enabling individuals of a given species to acquire and make use of the most appropriate information in a particular environment. Two examples of this are presented: learning of maternal odors in neonatal rabbits, including evidence that the sensory surface itself may be influenced by environmental conditions so as to enhance sensitivity to molecules of particular ecological relevance, and cross-cultural human studies suggesting that experience with everyday odors influences not only the way these are evaluated, but also their perceived intensity. It is concluded that an adequate understanding of odor coding and olfactory function will not be possible without taking such experience-dependent factors into account.
Abstract: In this study, 40 Japanese, 44 German and 39 Mexican women were presented with 18 everyday odorants. They were asked to rate them for intensity on a six-point scale from not detectable to very strong, for pleasantness on an 11-point scale from -5, to neutral at 0, to +5, and for familiarity on a six-point scale from completely unknown to extremely familiar. Consistent positive correlations were found between paired rating scores for the three measures, and although they were not particularly strong (r(s) range, 0.19-0.60), for most odorants all three correlations were significant. Similar results were obtained whether the data were analyzed on an individual or a national basis. Most notable were the consistent positive correlations between perceived intensity and ratings of familiarity and hedonic strength. It is suggested that the perceived intensity of the odorants depended not only on stimulus concentration but probably also on experience-dependent factors.
Abstract: Expression of c-Fos was examined in the olfactory bulbs of 3-day-old rabbits after they had been presented with the odour of garlic as a novel stimulus, as a learned odour, or during conditioning, and this expression compared with baseline levels in non-stimulated controls. Exposure to garlic odour resulted in substantial and widespread increases in c-Fos expression in the olfactory bulbs of all animals. However, although conditioned pups showed a specific behavioural response to the learned garlic odour, neither the amount nor pattern of c-Fos expression differed compared to pups exposed to garlic as a novel odour. The odour-induced expression of c-Fos was not well localised, although there was a significant increase in the number of granule cells expressing c-Fos in the ventrolateral region of the bulb. These results support previous reports that the response to odours in the olfactory bulb of new-born animals is not as spatially distinct as that in adults. Nevertheless, the immature olfactory system of these young animals is clearly capable of very specific odour learning.
Abstract: Although the rabbit (Oryctolagus cuniculus) continues to play an important role in the study of parturitional processes, a detailed behavioral description of birth in this species, necessary for accurately assessing the effects of experimental manipulation, is lacking. It is the aim of this report to provide such a description and to compare it with corresponding behavior in the better-studied rat. Ten pregnant chinchilla-breed rabbits and 10 pregnant Wistar rats were placed in glass-bottomed observation cages 2 days before term, and their behavior recorded on closed-circuit video, viewing the animals from below. All aspects of parturition were accomplished much faster in rabbits than rats; latency to birth of first pup, rate of delivery, duration of vaginal retention, time spent by mothers eating placentas, and in licking and nursing pups. In contrast to rat pups, rabbits were usually born separated from the placenta and already free from membranes. They were much more active, and well able to cast off any remaining membranes, suckle, and survive, whether directly attended to by the mother or not. We conclude that the tight temporal organization of events in the rabbit provides an unusually sensitive assay for investigating mechanisms underlying mammalian parturition.
Abstract: Despite the importance of chemosensation in the regulation of ingestive behavior, we still know surprisingly little about the development of the olfactory, trigeminal and gustatory systems. All three, however, are functional to some degree prenatally, and by birth infants are able to respond to a wide range of odors and can clearly distinguish between the tastes of sweet, sour and bitter. Based on findings from our work in the rabbit, we report that learning of odors associated with the mother's diet can occur very early in development, even prenatally, that it can have a long-term influence on later food choice, and may even lead to enhanced, stimulus-specific sensitivity of the basic sensory apparatus. Whether comparable phenomena exist in human infants is not known, although our recent findings that nationalities differ in judgements of the pleasantness of food odors depending on whether these are recognized as representing familiar, culture-typical foods, suggests that it might. A cross-cultural study is currently in progress examining the influence of culture-specific childhood eating experiences on adult preferences for food-associated odors.
Abstract: The high dimensionality and unpredictability of the chemical world makes it difficult for the olfactory system to anticipate relevant stimuli and construct neural filters accordingly. A developmental solution to this problem would be to alter the sensory surface according to environmental conditions so as to enhance sensitivity to molecules of particular relevance. Evidence for this has been obtained in the rabbit. By feeding pregnant does aromatic juniper berries, it could be shown that newborn, weanling and even adult animals demonstrate a preference for juniper odor without subsequent postnatal experience, and that this is associated with enhanced peripheral sensitivity for juniper odor as measured by electro-olfactogram (EOG). This is consistent with the report that in young salmon olfactory imprinting is associated with enhanced, odor-specific sensitivity of receptor cells as measured by patch clamp. The mechanisms underlying such changes are unknown, including the extent to which they are a particular feature of developing systems.
Abstract: Developmental studies of circadian function in mammals are generally difficult because of the close interaction between mother and young. The European rabbit presents an exception, providing developmental chronobiologists with an unusual opportunity to study the early development of circadian function. Doe rabbits only visit their newborn young once a day to nurse for a few minutes, and pups anticipate this regular event with heightened arousal and by uncovering of the nest. Both the mother's nursing visit and pups' anticipatory arousal represent well synchronized circadian rhythms. They also represent discrete, quantifiable events that can be readily manipulated by controlling does' access to the pups, by cross-fostering or by eliminating a nursing either before, during or after the development of visual function. The doe's long absence makes it possible to carry out surgical or other interventions without disrupting the normal pattern of maternal care, and the correspondence between pups' anticipatory arousal and the expression of c-Fos in hypothalamic nuclei demonstrates the suitability of this model for investigating the neural basis of early circadian function.
Abstract: Although morphological characteristics of mammalian olfactory bulb (OB) are well documented in rodents (rat, mice), only one study has been performed in rabbit, which is also commonly used in olfactory research. The study carried out by Allison and Warwick in 1949 led to surprising results still quoted in recent literature. The present study re-examined this question in young rabbit OB, while it was also conducted with rat as control. In five animals of each species, areas and coordinates of glomeruli and mitral profiles were measured in 10 coronal sections uniformly distributed along the rostrocaudal axis of the OB, and a distribution-free stereological method was used to compute values along this axis. For glomeruli, the estimated number was 4200 in rat and 6300 in rabbit. While this estimation matched with those found in literature in rat, it strikingly differed from the Allison and Warwick's value of 1900 only. For mitral cell number, we found 59,600 while the preceding study found 45,000 only. In contrast to the number of glomeruli, the mitral cell number in rat and rabbit were very close. Indeed, results showed 56, 200 in rat. The results suggest that the numbers of olfactory glomeruli and mitral cells has been previously underestimated in rabbit, and that the number of glomeruli changes as a function of species. In addition, both the results of the present study and reports in the literature suggest the number of mitral cells to be rather similar in mouse, rat and rabbit. As a consequence, the glomerular/mitral cell ratio is likely to varied in a wide range across species.
Abstract: There is a growing appreciation that experience with odors may strongly influence their perception. To further investigate this, the responses of 40 Japanese and 44 age-matched German women to everyday odorants were compared. Subjects were presented with 18 stimuli in squeeze bottles and asked to rate them according to intensity, familiarity, pleasantness and edibility, to describe associations elicited by them and, if possible, to name them. One-third of the odorants were presumed to be familiar to the Japanese only, one-third to the Germans and one-third to both populations. Significant differences were found between the two populations on all measures. Better performance by the Japanese in providing appropriate descriptors for 'Japanese' odorants and by the Germans for 'European' odorants supported the pre-selection of stimuli as culture-typical. Particularly clear differences between the two populations were found in pleasantness ratings. In general, a positive relationship was found between pleasantness and judgement of stimuli as edible, suggesting that culture-specific experiences-particularly of foods-may significantly influence odor perception. Somewhat unexpectedly, significant differences were also found between the two populations in intensity ratings for some odorants. These differences did not seem simply to be artefacts of the test situation and raise the possibility that experience may even influence such basic aspects of odor perception as stimulus intensity.
Abstract: To investigate the influence of experience on odor perception the responses of 40 Japanese and 44 age-matched German women to everyday odorants were compared. Subjects were presented with six 'Japanese,' six 'European' and six 'international' odorants and asked to rate them on intensity, familiarity, pleasantness and edibility, and to describe associations elicited by them, and if possible to name them. Significant differences were found between the two populations on all measures, with a close association of pleasantness ratings and edibility judgments suggesting the particular influence of eating habits on odor perception. Positive correlations between familiarity and pleasantness, strength of hedonic judgment and intensity, and familiarity and intensity were also found in both groups and for most individuals. The generality of these findings was supported by the results obtained from testing 40 Mexican women with the same odorants.
Abstract: Rabbits exhibit an unusually restricted form of maternal care. The newborn young are only nursed for about 3 min every 24 h and drink up to one third of their body weight in this time. They show a circadian increase in activity in anticipation of the doe's visit, which is entrained by suckling and appears analogous to feeding-entrained rhythms reported for other species. By investigating the expression of c-Fos protein in nursed and un-nursed pups at selected times before and after scheduled nursing, we were able to distinguish endogenous patterns of neuronal activation and patterns induced by suckling. Increased endogenous expression of c-Fos in the paraventricular thalamus and in the magnocellular neurons of the paraventricular hypothalamus coincided with the period of anticipatory arousal. By contrast, suckling induced c-Fos expression in the supraoptic nucleus and the parvocellular neurons of the paraventricular hypothalamus, whilst decreasing expression in the magnocellular neurons. Furthermore, the endogenous pattern of c-Fos expression was less distinct in 3-day-old compared to 7-day-old pups, suggesting maturational or experience-related influences on the neural correlates of the anticipatory arousal. In conclusion, the close correspondence between c-Fos expression and pups' endogenous rhythm of behaviour suggests that the rabbit's natural schedule of restricted nursing provides an ideal model in which to investigate the ontogeny of circadian function without disrupting the mother-offspring relationship or normal neonatal development.
Abstract: In the rat the pelvic nerve consists of a viscerocutaneous (sensory) branch which receives information from pelvic viscera and the midline perineal region, and a somatomotor (muscular) branch which innervates the ilio- and pubococcygeous muscles. To investigate the contribution of these branches to the parturition process, the length of gestation and course of delivery were closely monitored in 43 pregnant, Wistar-strain rats randomly assigned to five groups: untreated control animals, animals in which the somatomotor branch of the pelvic nerve was bilaterally sectioned on Day 14 of gestation, animals in which the viscerocutaneous branch of the pelvic nerve was bilaterally sectioned on Day 14 of gestation, animals treated similarly to the previous group but with young delivered by C-section at term, and sham-operated controls. Sectioning the viscerocutaneous branch seriously disrupted parturition and resulted in major dystocia and a high percentage of stillbirths in all females. In contrast, sectioning the somatomotor branch had no apparent effect on parturition and no significant differences were found between females of this group and sham or control dams on any of the measures recorded. It is concluded that the viscerocutaneous branch of the pelvic nerve is vital for the normal course of parturition in the rat but that the somatomotor branch plays little role, if any.
Abstract: Twenty congenitally anosmic subjects and 50 normosmic controls were tested for their ability (i) to assign verbal labels from a list of trigeminal-type descriptors to six odorants believed to have a strong trigeminal component; and (ii) to discriminate between intensity-matched pairs of these odorants in an odd-ball paradigm. The following was found: normosmic controls judged menthol and cineole as distinctly cool and fresh, acetic acid as pungent and sour, and acetone as pungent, but showed no clear descriptive profile for ethanol and propanol. The descriptive profiles given by the anosmic subjects correlated significantly with those given by the controls for three of the six odorants (menthol, cineol and ethanol), confirming that the sensations described may indeed be mediated by the trigeminal system. In the odd-ball test, the control subjects correctly identified an average of eight out of the nine items presented, with most mistakes occurring in response to pairs with a similar trigeminal profile. With an average of 7.2 of nine items correct, the performance of the anosmic subjects was not significantly different to that of the normosmics, except in discriminating between acetic acid and menthol. Although additional tests are necessary to decide finally whether differences in stimulus intensity may have contributed to this good discriminatory performance, the present results suggest that the nasal trigeminal system may contribute significantly to the perception of odor quality.
Abstract: European rabbits (Oryctolagus cuniculus) of both sexes possess a variety of skin glands important in chemical communication. These include sizable inguinal glands, the strong-smelling secretion from which accumulates in conspicuous pouches of skin on either side of the genital opening. To test the hypothesis that this secretion advertises sexual receptivity in females, inguinal gland secretions from nine intact and six ovariectomized females were presented on dummy rabbits or in a simultaneous choice paradigm, and the responses of nine stud males to these secretions were recorded. Although the males clearly perceived the stimuli, no differences in responses to secretions from the intact and ovariectomized does were observed, and no differences were found in the size, weight, or secretory activity of the does' glands. It is concluded that inguinal gland secretion plays little role in communicating sexual receptivity in female rabbits and that ovarian steroids play little part in regulating inguinal gland activity.
Abstract: Chin marking by the European rabbit (Oryctolagus cuniculus) is one of the classic but still little understood examples of mammalian chemical communication. To investigate whether the sexes differ in performance of this behavior, we compared the frequency of spontaneous chinning and chinning in response to the chin marks of conspecifics in 20 intact male and 20 intact female chinchilla-breed rabbits, and in five gonadectomized animals of each sex. Contrary to the expectation of greater chinning activity in males, no significant sex differences were found. Frequencies of spontaneous chinning were similar in the two sexes, large and stable individual differences were observed in both, chinning increased in both when marks from unfamiliar conspecifics were present, and both directed chin marks to objects marked by conspecifics more than to unmarked objects. Individual chinning frequencies correlated positively with urination but not defecation in both sexes, and spontaneous and odor-induced chinning were significantly reduced both in castrated and ovariectomized animals. The findings suggest that chinning is an equally significant part of the communication system of male and female rabbits and that its expression may be regulated by similar olfactory, hormonal, and social mechanisms.
Abstract: Despite the importance of the rabbit (Oryctolagus cuniculus) in reproduc¬tive research, no comprehensive account of the anatomical organization of the female reproductive tract is presently available. Based on gross dissection and on the electrical stimulation of striated muscles in eight domestic females, it was the aim of this study to help fill this gap by describing the origin, insertion and general action of muscles associated with the vaginal tract, together with associated scent glands. Compared to the better-studied rat or cat, the long vaginal tract of the rabbit was characterized by a well-developed and complex musculature. The bulbospongiosus, ischiocavernosus, constrictor vestibuli and constrictor vulvae muscles, poorly developed or absent in the female rat or cat, were particularly conspicuous. Scent glands, including the newly identified preputial glands, were also a distinctive feature of the tract and pelvic region. It is suggested that these structures may represent specializations underlying the rapid copulation, rapid parturition, and well-developed chemical communication characteristic of the reproduc¬tive efficiency of the rabbit.
Notes: -Translation of:
(1996) Just three minuts a day: The behaviour of young rabbits viewed in the context of limited maternal care. In:Proc 6th World Rabbit Congress Vol 2 Edited by:F Lebas, M Verga. 395-403 Lempdes, Tolouse
Abstract: Maternal care in the European rabbit, Oryctolagus cuniculus, is limited to one brief nursing visit a day. To investigate the nature of this unusual mother-young relationship, four domestic does and their litters were raised separately except for the once-daily nursing, and the following parameters were recorded; from post-natal days 1 to 30, the duration of nursing bouts, daily milk yield, deposition of faecal pellets in the nest by does, daily weight gain of pups, eating of faecal pellets and nest material by pups, their water intake, and from post-weaning days 31 to 44, their weight gain. Does were mated immediately after giving birth, and the measures for the first litters raised when does were pregnant were compared with the results for the second litters raised when does were not pregnant. Four control does and their litters were treated in the same way but without separating mothers and young. In all litters pups progressed from drinking milk alone, to nibbling faecal pellets, to ingesting nest material, drinking water and finally eating food pellets. However, growth rates and the pattern of weaning depended on does' reproductive state. The first litters, raised by pregnant does, were significantly lighter and were weaned earlier than the second litters raised by the same does when not pregnant. The rabbit thus provides a particularly good opportunity to investigate mechanisms underlying reproductive decision making and developmental strategies in an unusual mother-young system.
Abstract: Responsiveness to pain was determined in female rats across the whole reproductive cycle using the tail-flick test. When tested immediately after mating, pain thresholds were unaltered, whereas 10 min later animals typically demonstrated hyperalgesia (Experiment 1). They also demonstrated hyperalgesia during most of pregnancy, and had significantly lower pain thresholds than the unmated controls except for the 24 h before parturition, when a sudden increase in tail-flick latencies was recorded (Experiment 2). Pain thresholds were also significantly lower throughout the nursing period but increased significantly when dams were separated from their litters for 6 h, and returned to premating baseline values within 24 h of weaning (Experiment 3). These findings confirm and extend earlier reports that female reproductive state may significantly modify responsiveness to noxious stimuli, and it is suggested that differences between the results of this and previous studies may be at least partly explained by the relatively stress-free test procedure adopted here.
Abstract: Olfactory function was assessed in 20 women during each trimester of pregnancy and post partum, and compared with that of 20 non-pregnant women tested in parallel. In contrast to earlier reports, no consistent differences in olfactory sensitivity or odor evaluation were found between the two groups.
Abstract: Five squirrel monkeys (Saimiri sciureus) were trained to discriminate between pairs of odors, and their ability to recognize these as positive or negative was tested at intervals of up to 7 months. Retention was excellent up to 15 weeks and remained significantly above chance even after 30 weeks. Good performance at the shorter intervals was not due to rapid relearning, although at the longer intervals considerable savings were demonstrated by the animals' ability to reach criterion more rapidly than with novel odors. Thus, squirrel monkeys possess a robust memory for odors and show flat forgetting curves consistent with reports for human subjects.
Abstract: Rabbits nurse briefly only once each night and are frequently both pregnant and lactating. To investigate the influence of the daily timing of nursing on parturition, does (n = 10 per group) were remated after giving birth and were allowed to nurse under one of three schedules: group 1 every 24 h in the light, group 2 every 24 h in the dark, and group 3 at any time. Whereas does from groups 2 and 3 nursed and gave birth normally, does of group 1, forced to nurse out of phase with the normal schedule, showed disturbed nursing behavior and prolonged gestation followed by many stillbirths. In a second experiment, pregnant does (n = 10 per group) were treated daily either with oxytocin (OT) in the light (group 4), with OT in the dark (group 5), or with progesterone (P; group 6) or saline (group 7) in the light. All does gave birth normally except those of group 4, which responded similarly to group 1 does. These findings demonstrate that in the rabbit, parturition may be seriously compromised if does nurse out of phase with the normal schedule and suggest that a shift in the daily timing of OT release may underlie this.
Abstract: In this study, an odour-conditioning paradigm was used to investigate the ability of captive squirrel monkeys, Saimiri sciureus, to discriminate between urine odours of conspecifics. It was found that the three test females could: 1. Readily discriminate between urine from conspecifics and other primate species; 2. Discriminate between urine from individual conspecifics, whether unfamiliar animals or members of the test animals' social group, and whether or not they were of the same sex; and 3. Not discriminate so easily between urine from genetically related conspecifics as between urine from unrelated individuals, particularly where both donors were female. The findings suggest that an individually distinct and stable factor is present in squirrel-monkey urine, that this is more similar in genetically related than unrelated individuals, and that, in males, some additional source of individual variability exists enabling the discrimination of even close relatives. While the biological significance of these findings remains to be investigated, this study demonstrates that squirrel-monkey urine contains a considerable amount of information of potential signal value.
Abstract: Choosing an appropriate diet raises special problems for generalist herbivores, especially in areas where most of the plant species are poisonous. This was the case in our study site, the Bugac Juniper Forest (Kiskunsag National Park, Hungary). The main herbivore of this forest, the wild rabbit (Oryctolagus cuniculus), can choose from about 70 plant species, but several of these are toxic or only of medicinal value. Moreover, even the nutritious species of the sparse vegetation are available only for short periods. The annual mortality rate is extremely high for the young, only those individuals survive that can find suitable places to hide and the least poisonous plants to eat. This selection pressure might force the pups to get information about the edible food types as early as possible, i.e. in the nest from their mother.
This hypothesis was experimentally tested using domestic, chinchilla-breed rabbits. Three groups of females were kept on three different diets during the gestation and lactation periods. Just after weaning, food choices of differently treated mothers' pups were tested in a three-way food-choice test lasting 1 wk. The first choices were registered and the amount of food eaten from the different food items was measured during each test session. Analysis of the results of the first choices revealed that the animals started to eat the same food their mother had eaten during pregnancy and lactation. Analysis of the consumed amounts also supported this finding. Pups of treated mothers significantly preferred the aromatic plants their mother had eaten previously, even if it caused serious disadvantages to the young by reducing the number of offspring and increasing the mortality rate of the pups. The results of these experiments suggest that food preferences in wild rabbits can be transmitted from one generation to the other by social learning, although, to keep a balanced diet in an ever changing environment, individual experience and learning are indispensable.
Abstract: Pain threshold was determined in female rats using the tail flick test. Latency to respond depended on the locus of the tail heated, with the most distal sites resulting in the shortest response times (Experiment 1). Tail flick latency also varied according to the time of day, with shorter response times recorded around the middle of the dark phase than near its beginning or after its end. This was the case for intact, for ovariectomized, and for ovariectomized, estradiol-treated rats (Experiment 2). However, response times also varied across the estrous cycle, with significantly shorter latencies recorded during estrus and metestrus. Ovariectomy abolished these fluctuations, and whereas administration of estradiol increased response times, progesterone had little effect (Experiment 3). These results suggest that site of tail heating, time of day, and presence of ovarian hormones can influence tail flick latency independently, thus demonstrating the complexity of the mechanisms that may contribute to pain threshold even within the same paradigm.
Abstract: Using ovariectomized New Zealand white rabbits and the nipple-search behavior of pups as a bioassay, we evaluated the capacity of prolactin to stimulate the emission of an odor signal that allows newborn pups to locate the mother's nipples and suckle. Whereas emission of this so-called nipple pheromone was minimal in untreated, ovariectomized does, emission was stimulated by the administration of progesterone (1 mg/day) to estrogen-treated does (0.5 microgram estradiol benzoate/day) and decreased after withdrawal of progesterone despite continuous administration of estrogen. However, substituting ovine prolactin (1.5 mg/day) for progesterone, under continuous estrogen administration, resulted in an increase in pheromone emission to near-maximal levels. This stimulatory effect of prolactin was not progesterone-dependent since it also occurred in does pretreated with estrogen alone and, to a lesser extent, even in females without estrogen priming. From these and previous data, we propose that emission of nipple pheromone in the rabbit is induced during pregnancy by the combined action of estrogen and progesterone, and maintained during lactation by the dual action of estrogen and prolactin.
Abstract: Hypogonadotropic hypogonadism (HH) refers to an endocrine defect of hypothalamic origin resulting in gonadal hypoplasia and frequently associated with anosmia or severely impaired olfactory function (Kallmann's syndrome). This apparently results from a disruption in the migration of neurons from the olfactory placode to the bulb and hypothalamus early in development, and so provides a unique opportunity to investigate olfactory function in human subjects with congenitally incomplete peripheral systems. Olfactory performance in 37 HH patients and 37 age-matched controls was compared using a modified version of the Munich Olfaction Test. This test is based on the sniff-bottle method and includes tests of (i) odor quality discrimination, (ii) intensity discrimination, (iii) detection thresholds, and (iv) recognition, hedonic evaluation and identification ability. The patients could be divided into two distinct groups differing significantly on all four subtests and showing no overlap in performance: 20 anosmics, conforming to Kallmann's syndrome, and 17 apparent normosmics whose performance was slightly poorer, but not significantly different to that of the controls. The unexpected failure to find a continuum of olfactory dysfunction now raises the question whether HH with or without anosmia represents two syndromes with distinct etiologies, or rather reflects the ability of the olfactory system to function well despite morphological impairment.
Abstract: Results from experiments on two strains of domestic rabbit show that despite their hopping gait, circadian locomotor rhythms can be successfully measured using running wheels specially designed for large laboratory mammals. Three female rabbits of an English outbred strain were monitored in a 13:11 light:dark (LD) cycle and in constant light (LL), while 12 Dutch-Himalayan rabbits were monitored in a 14:10 LD cycle and constant dark (DD). Much stronger rhythms were observed in the latter strain, which under LD conditions showed individuals with patterns that varied from nocturnal (n = 5), diurnal (n = 4), crepuscular (n = 1), and predominantly arrhythmic (n = 2). In DD, 10 rabbits showed strong free-running rhythms, five with tau (tau) less than 24 h and five longer. The predominantly arrhythmic activity pattern in the remaining two made estimation of tau difficult. Differences in circadian patterns both under LD and DD were unrelated to sex. Results show that locomotor rhythms of the rabbit can be measured using the running wheel, the traditional apparatus of chronobiology. However, the experiments suggest also that the large-bodied breed of rabbits that tend towards obesity, such as the English outbred strain, are relatively inactive and that smaller, more active breeds such as the Dutch-Himalayan may be more suitable for studying circadian rhythmicity if the running wheel is employed.
Abstract: After being nursed just once for 4-5 min by an artificially scented doe, newborn rabbits show the full pattern of nipple-search behavior when placed on a fur scented with the same odor as their mother. It was the aim of the present study to test whether such rapid learning is dependent on age. In Experiment 1 in which normally raised pups were nursed by a scented doe either on Days 1, 3 or 5, conditionability was found to decline markedly by postnatal Day 5. In Experiment 2 conditionability was maintained in pups deprived of suckling experience by bottle feeding from Days 1-4, but not in hand-raised pups allowed to search on a doe for 4 min daily without milk intake. Possible mechanisms underlying the decline in conditionability to suckling odors, as well as the potential functional significance of this early learning for immediate postnatal and later life are discussed.
Abstract: It was the purpose of this study to test whether inhibition of estrus in the rabbit by short photoperiod could be simulated by subcutaneous implants of the pineal hormone melatonin. By measuring two non-invasive and readily quantifiable correlates of estrus, emission of the so-called nipple-search pheromone and scent-marking behavior (chinning), it was found that: 1. In intact does kept in stimulatory long photoperiod, melatonin suppressed chinning but had no effect on emission of nipple-search pheromone. 2. In intact, melatonin-treated does which were returned from inhibitory short day to stimulatory long day, chinning remained suppressed, whereas pheromone emission increased as for the vehicle-treated, control does. 3. In ovariectomized does, estradiol administration stimulated both pheromone emission and chinning whereas melatonin failed to suppress these effects. Thus, although the administration of melatonin had an inhibitory effect on chinning it failed to suppress emission of the nipple-search pheromone and therefore failed to fully simulate the effect of short photoperiod on these two correlates of estrus. Several explanations for this discrepancy are considered, including the possibility that melatonin is not the sole mediary of the photoperiodic response, and that at least in female rabbits, other pineal products may also play a significant role.
Abstract: Rabbit pups raised by mothers fed different diets during pregnancy and lactation show a clear preference for the diet of their mother at weaning. By supplementing does' lab chow diet with aromatic juniper berries, the present study aimed to investigate the relative importance of 1) fecal pellets deposited by the mother in the nest, 2) prenatal experience in utero, and 3) contact with the mother during nursing in determining pups' later food preference. The three means of transmission were found to be equally effective. Thus, pups from normally fed does raised with fecal pellets from juniper-fed mothers, pups from juniper-fed mothers cross-fostered to normally fed does immediately after birth, and pups of normally fed mothers nursed by juniper-fed does all showed as strong a preference for juniper as pups raised by juniper-fed mothers exclusively. Such apparent redundancy may not only help insure that less aromatic substances or substances transmitted differentially by these routes are learned, but also that pups can acquire a preference for a variety of foods eaten by their mother at different times.
Abstract: The term imprinting is used to refer to biologically relevant learning during a sensitive period defined by a particular developmental stage or physiological state. Although olfactory imprinting may occur at any age, and some of the best-studied paradigms involve adult animals, recent reports of long-term memory for odorants experienced during prenatal life present a particular challenge to our understanding of olfactory learning. Firstly, it is possible that these paradigms represent a form of exposure learning based on mechanisms different to the more familiar associative paradigms. Secondly, given the substantial addition of neural elements occurring during the perinatal period, these paradigms raise the question as to how the olfactory system, and eventually the brain, is able to acquire and retain information under conditions of major neural growth and change.
Notes: Translation (modified and extended):
(1995) Funktionelle Bedeutung und neuronale Mechanismen der Geruchsprägung. In:Bericht über den 39 Kongreà der Deutschen Gesellschaft für Psychologie in Hamburg 1994 Edited by:K. Pawlik. 324-328 Hogrefe Verlag, Göttingen, Germany
Abstract: In a task designed to simulate olfactory-guided foraging, the ability of squirrel monkeys to discriminate an artificial 12-component odorant from 3-, 6-, 9- or 11-component submixtures was investigated. A combination of factors was found to contribute to the animals' performance: 1. Discriminability generally decreased as the number of components in the submixture increased. 2. Submixtures did not contribute equally to mixture perception, and one component in particular (cineole) disproportionately influenced stimulus discriminability. 3. Interactive effects between submixtures resulted in marked deviations from the general pattern of discriminability. 4. Changes in the relative concentration of submixtures could also influence discriminability. 5. Finally, individual differences in responsiveness to particular stimuli were apparent. These findings demonstrate that the interaction between components in odor mixtures can be complex and that seemingly small changes in composition can strongly affect perception and thus potential signal function. It is therefore suggested that in future investigations of squirrel monkey semiochemistry, the method of systematically varying submixtures may be particularly useful in defining the contribution of components to a signal.
Abstract: Using a task designed to simulate olfactory-guided foraging behavior, this study demonstrates for the first time that olfactory performance can be reliably assessed in squirrel monkeys. Small flip-top vials were fixed in random order to the arms of a climbing frame and equipped with odorized strips signalling either that they contained a peanut food reward (S+) or that they did not (S-), and three adult female monkeys were allowed 1 min to harvest as many baited nuts from this tree as possible. Given five 1-min trials per day, animals took between 15 and 25 days to reach the criterion of 80% correct choices, could readily transfer to new S+ or S- stimuli, and could remember the task even after a 1-month break. The precision and consistency of the monkeys' performance in tests of discrimination ability and sensitivity demonstrate the suitability of this paradigm for assessing olfactory function, and a first test of human subjects using the same cups and odorants showed that it may also be used to directly compare olfactory performance in human and nonhuman primates.
Abstract: The purpose of this study was to investigate (i) the ability of human subjects to detect changes in related odor mixtures following omission of components, and (ii) the possible relationship between the number of substances comprising a mixture and the ability to detect changes in its composition. A total of 36 panelists was tested repeatedly in five separate sessions using sniff bottles, and asked to rate the difference between pairs of stimuli using a 6-point verbal scale. Stimuli were 3-, 6- and 12-component mixtures paired with stimuli from which one or more of the components had been omitted or had been left unchanged. Rating behavior was highly consistent, with no significant differences found between sessions or panels in judging the identical control pairs. Although asymmetrical pairs were judged to be different significantly more often than control pairs, correct assignment was considerably poorer than expected. Correlations between complexity of a stimulus and ability to discriminate changes in its composition were weak and possibly confounded by substance-specific, synergistic effects. While factors such as lack of feedback or the arbitrary nature of the stimuli may have affected performance, it remains to be investigated whether the findings indeed reflect our limited capacity to discriminate between related odor mixtures.
Abstract: In the European rabbit, Oryctolagus cuniculus, chin marking is one of the most conspicuous forms of olfactory communication. In an investigation of factors influencing the expression of this behaviour in females, the marking frequency of seven intact and three ovariectomized does was tested over a 12-month period by placing them individually for 10 min each day in an arena containing three bricks. In the intact does but not in the ovariectomized ones, the frequency of chinning was increased by experimental long days and suppressed by experimental short days within 1â2 weeks of reversing the light regime. These changes were accompanied by clear alterations in the size and colour of the vulva, indicating that oestrus was also suppressed under the short-day conditions. However, presenting does with bricks marked by donor animals resulted in a significant increase in the frequency of chinning independent of photoperiod. Moreover, does appeared to distinguish between donors, directing marks preferentially to bricks marked by males rather than females, bricks marked by long-day rather than short-day donors, and those marked with chin gland secretion rather than with donors' urine or with carrot or lemon juice. Thus, while the finding that chinning activity was positively correlated with oestrus is consistent with the hypothesis that in females this behaviour is a form of sexual advertisement, the differential response shown to the chin marks of individual donors, even by non-oestrous does, suggests other, non-sexual functions for the chemosignals in chin gland secretion.
Abstract: Rabbit pups are completely dependent on a maternal pheromone for the release of suckling behavior. However, if the mother is perfumed prior to nursing, pups will learn to respond to the novel odor with the characteristic nipple-search behavior in just one 3-4 min nursing episode. In a first investigation of the processes underlying this recently developed learning paradigm, time-dependent effects of hypothermia on retention of the task could be demonstrated. Thus pups whose whole body was cooled to a mouth temperature of 7 degrees C immediately after conditioning (n = 10) and tested 24 h later for 3 min on a perfumed fur did not differ significantly in their search response from naive, untreated controls (n = 10). In contrast, pups cooled 4 h after conditioning (n = 10) demonstrated clear retention of the learned response and searched as vigorously as conditioned but uncooled animals (n = 10). As pups of all groups demonstrated normal nipple-search behavior when tested on a lactating doe, the deficits associated with immediate cooling appear to have been specific to the learning task and time of treatment.
Abstract: It was the purpose of the present study to investigate whether the perception of odour mixtures differs from the perception of their components with regard to (i) the reliability of detection threshold measurements and (ii) the threshold values themselves. Detection thresholds for a variety of unmixed odorants and 3-, 6- or 12-component mixtures were determined for a total of 44 subjects, tested repeatedly in five separate sessions using sniff bottles and an ascending staircase method. Threshold determinations for the mixtures were found to be as reliable as for the unmixed substances, with intra- and interindividual variability in threshold values actually decreasing with increasing stimulus complexity. The four mixtures for which a systematic comparison of the threshold values of components in the mixed and unmixed state was conducted failed to provide evidence for the hypo-additive effects of compromise or compensation, but rather suggested a positive, sub-threshold interaction between components and possibly even enhancement. Finally, a significant improvement in individual threshold scores was seen across test sessions, with experienced panelists showing the most stable performance.
Abstract: To suckle, newborn rabbits are completely dependent on a pheromone present on the doe's ventrum and also apparently contained in the milk. Pups presented in a standardized test with 30 microliters of fresh rabbit milk on a glass rod reacted with vigorous search-like movements in 93%, and with grasping of the rod in 70% of trials, but did not respond to control presentations of other odorants. The pups were found to be most reactive 1-3 hours before the once daily nursing, and although they rapidly habituated to repeated testing, a break of 30 minutes was sufficient for the recovery of responsiveness. Even milk diluted by as much as 1:10(4) elicited significantly more responses than control substances. However, when left at room temperature it lost this behavior-releasing quality within about 20 minutes, but retained it for several months when stored at -40 degrees C. Rabbit milk thus appears to represent a ready source of nipple-search pheromone, and the behavioral response of pups to be reliable enough to serve as a bioassay for further pheromonal analysis.
Abstract: As part of a study of the development of olfactory function in the rabbit, a morphometric analysis of the olfactory epithelium in newborn and 30-day-old animals was carried out. Surface area, thickness and cell densities of the olfactory epithelium were compared in hematoxylin-eosin stained serial sections through the nasal cavities of 4 newborn and 3 weanling rabbits. While the basic structure of the olfactory cavity changed little with age, a large quantitative development in the epithelium was observed. The pattern of growth appeared uniform and resulted in a 3-fold increase in total surface area from about 1 cm2 per side in the newborn to about 3 cm2 in the weanling, and an increase in thickness from approximately 65 microns to about 90 microns. The increase in thickness was due mainly to a disproportionate, 5-fold increase in the number of olfactory neurons. This resulted in a total of about 32 million cells per side by day 30, and represented an increase in the ratio of neurons to basal cells of 7:1 to 10:1, and neurons to supporting cells of 2:1 to 4:1. While such an increase in the number of primary neurons presumably improves the animal's perceptual abilities, it nevertheless raises the question as to how perceptual constancy can be maintained during a period of such rapid neural change.
Abstract: To investigate environmental influences on the development of the olfactory epithelium, semi-thin sections were taken from the nasal septum of newborn and 30-day-old rabbits; the epithelial thickness and the number of olfactory knobs, supporting cells, dark basal cells, and receptor cells were compared. During normal development, a marked increase in epithelial thickness was found, largely because of an increase in the number of receptor cells. Whereas unilateral nare occlusion on day 1 resulted in 10% fewer receptor cells and 25% fewer knobs on the deprived side by day 30, nare occlusion either up to or after day 5 had little effect, and even temporary reopening from days 6-7 was sufficient to stimulate receptor-cell development on the occluded side. Although in these latter cases, a slight deprivation effect of 6% was still found in the number of receptor-cell nuclei, there was no longer a significant difference in the number of knobs between the open and closed sides. Thus, whereas exposure to the environment during the first days of life appears to be sufficient to stimulate sustained growth, the deprived epithelium may retain the capacity to respond to such cues beyond this time. However, as nare occlusion also had an effect on the respiratory epithelium and nasal lymphatic tissue, the nature of the cues stimulating receptor-cell development, whether olfactory or non-olfactory, is not yet clear.
Abstract: Newborn rabbits are completely dependent on a pheromone on the mother's belly for the release of nipple-search behaviour and suckling. Using the stereotyped behavioural response of the pups as a bioassay it could be shown that: 1. In non-breeding does pheromone emission is stimulated by experimental long day and suppressed by experimental short day conditions within 1 to 2 weeks of reversing the light regime. 2. Under constant long day conditions pheromone emission, readiness to mate, conception rate and litter size remain high with no evidence of endogenous seasonal rhythmicity. 3. Experimental changes in daylength of just 1 or 2 h in either direction are sufficient to induce marked alterations in the level of pheromone emission, number of successful matings and average litter size within 2 to 3 weeks. Pheromone emission would thus seem to provide a sensitive test of photoperiodic responsiveness in non-breeding female rabbits, and a convenient, non-invasive indicator of their reproductive state.
Abstract: Kaninchen säugen ihre Jungen nur einmal pro Tag, für nur 3-4 Minuten. Um in dieser kurzen Zeit genügend Milch zu erhalten, haben die Jungen eine Reihe von Verhaltensanpassungen entwickelt, die sie für Untersuchungen olfaktorischer Funktionen besonders geeignet machen. So löst ein Pheromon, das von der Mutter produziert wird, bei neugeborenen Kaninchen angeborenermaÃen ein stereotypes Zitzensuchverhalten aus, doch sie auch während eines einzigen Säugens einen neuen Geruch erlernen, auf den sie dann mit dem gleichen Suchverhalten reagieren. Dieses Verhaltensmodell erlaubt es, in einfacher Weise neurobiologische Mechanismen der Geruchswahrnehmung und des Geruchslernens experimentell zu untersuchen.
Abstract: In four fruit-eating bats sniff-rate analysis revealed the threshold value for natural banana odour to be 1 Ã 10â4 vol% of head-space while the threshold values for its major components were found to be 3â6 orders of magnitude higher; even the total of molecules present at the threshold dilution of banana odour was 2 orders of magnitude below the lowest threshold values obtained for single components. Thus, the responsiveness of the bats to threshold concentration of natural banana odour is discussed as an example of synergism of stimuli.
Abstract: The effect of daily injections of estradiol benzoate (1 or 10 micrograms) and of progesterone (10 mg) on chin marking activity, sexual receptivity, and emission of nipple-search pheromone in ovariectomized rabbits was investigated. Both estradiol treatments resulted in a significant increase in all three measures over baseline and control group levels within 1-3 days, and withdrawal in a return to pretreatment levels within 2 weeks (Experiment I). In contrast, the administration of progesterone to such estradiol-primed does resulted in an almost immediate suppression of chin marking and lordosis, but in marked enhancement of pheromone emission and aggressive behavior (Experiment II). However, progesterone given alone to nonprimed does had no effect on any of these measure (Experiment III). The response profiles resulting from these treatments correspond well to patterns reported for intact does during estrus (= estradiol alone), pregnancy (= estradiol plus progesterone), and at parturition (= progesterone withdrawal).
Abstract: Zahlreiche Untersuchungen weisen darauf hin, daà die meisten physiologischen und viele psychologische Parameter einen Tagesrhythmus haben. Diese Tatsache ist von klinischer Bedeutung, jedoch kommen unsere chronobiologischen Kenntnisse vor allem dem erwachsenen Patienten zu Gute, da die Onto-genese der circadianen Rhythmen bisher nur wenig erforscht wurde. Dieser MMW-Report gibt einen Ãberblick über den gegenwärtigen Stand des Wissens und diskutiert mögliche Konsequenzen für die Säuglingspflege.
Notes: - reprinted: (1994) In J Zulley, E Haen, R Lund und T Roenneberg (Hrsg) Chronomedizin Roderer Verlag, Regensburg: Vol 1: 147-155
Abstract: In newborn rabbits, small and apparently arbitrary regions of the olfactory bulb and associated epithelium appear capable of a high degree of odor processing. After medial or lateral removal of up to 80% of the olfactory bulbs, including the accessory bulb, newborn pups were still able to respond appropriately to the pheromone-governing suckling behavior (Expt. I), could rapidly learn to associate a novel, artificial odor with suckling (Expt. II), and continued to respond appropriately to artificial odors learned prior to lesioning (Expt. III). These findings suggest that the perception and recognition of such suckling signals does not depend on the integration of information from the entire bulb or epithelium, and question the extent to which patterns of 2-deoxyglucose uptake in the bulb reflect the neural coding for specific odors. However, as the tasks set here only required detection of odor signals and not true odor discrimination, it may still be that the full bulbar pattern of activation is necessary for higher-order processing, such as distinguishing between odors and attributing different meanings to them.
Abstract: Newborn rabbits are completely dependent on a pheromone present on the mother's belly for the release of the highly stereotyped nipple-search behavior and for nipple attachment. Surgical removal of the vomeronasal organ had no effect on pups' ability to respond to the pheromone when tested on a lactating female, nor on their ability to obtain milk in the normal nursing situation. Lesioned pups could also learn to associate the odor of citral with nipple-search behavior when nursed by a citral-scented doe. In contrast, irrigating the nasal mucosa with ZnSO4 completely eliminated responsiveness both to the pheromone and to the conditioned odor of citral. This is of particular interest given the important role attributed to the accessory olfactory system in pheromonal perception. However, it might be necessary to distinguish between pheromones associated with suckling and therefore peculiar to mammals, and other pheromones.
Abstract: Behavioral teratologists interested in extending the range of animal models which might be used to investigate teratogenic or developmental toxic effects on behavior, might do well to consider the rabbit. As a traditional laboratory animal the rabbit has the usual advantages of being cheap to maintain and notoriously easy to breed, producing good sized litters of relatively large, fast growing altricial young, in addition, and of particular importance in teratology, induced ovulation in this species allows the precise determination of gestational age. Above all however, the unusual lack of maternal care would seem to make the rabbit a particularly promising subject. The purpose of this report is to provide a brief outline of the behavior of rabbit pups resulting from its limited maternal input. While the basic patterns appear in many respects similar to those already described for the more thoroughly studied rat, it will be argued here that the unusually fast and highly stereotyped performance of much of the behavior, together with the minimal interference of the mother, should make the newborn rabbit a useful addition to animals commenly available to behavioral teratologists.
Abstract: Rabbit pups do not need to learn postnatally the pheromonal cues releasing nipple-search behavior. Pups delivered by caesarian section were able to attach to nipples as quickly as normally delivered controls in their first encounter with a lactating doe (Experiment I), and pups hand raised to Day 5 without postnatal experience of the nipple-search pheromone even showed an improvement in their reactivity to it similar to normally raised controls (Experiment II). However, 1-day-old pups could be conditioned during the first nursing episode to respond with nipple-search behavior to artificial odors painted on the mother's ventrum (Experiment III). Finally, pups conditioned on Day 1 but subsequently raised by hand or normally nursed showed retention of the conditioned responsiveness when tested on Day 5 (Experiment IV). These experiments suggest that although rabbit pups are capable of rapidly associating odors with suckling, they do not appear to depend on this ability under normal nursing conditions.
Abstract: By performing uni- and bilateral olfactory bulb lesions and uni- and bilateral transsections of the infraorbital branches of the trigeminal nerves in 2-day-old rabbits, it could be shown that: Both the olfactory and tactile modalities are essential for the successful performance of nipple-search behaviour. While bilateral bulbectomy completely eliminates searching, and hence suckling, unilateral bulbectomy has relatively little effect. Bilateral denervation of the muzzle does not eliminate searching, but pups are unable to suckle as they fail to show the mouth-opening component necessary for nipple attachment. In contrast to unilateral bulbectomy, unilateral denervation of the muzzle results in a lateralization of head movements during searching, nipple grasping and nipple release.
Notes: - Translation: (1985) Wenn beim Säugen die Sekunden zählen. Forschung 85: 1. 22-23
- Reprinted: (1986) Das Blaue Kaninchen-Jahrbuch 1986, Deutscher Kleintierzüchter, Reutlingen, 81-83
Abstract: Developmental changes in the nipple-search behaviour of rabbit pups (Oryctolagus cuniculus) were investigated from day 1 to day 13. The performance of four litters was tested 1 h before and 6 h after the once-daily nursing, and of two litters 6 h before and 1 h after nursing on lactating does restrained on their back. During the first 5 days, the median times taken by pups to attach to nipples decreased from 11.8 s to 3.2 s. This improvement was mainly due to a decrease in the latency to search and suggested an improvement in the ability to react to the nipple-search pheromone. Except for the first day, pups located nipples faster before than after nursing, and were best 1 h before. After the first week, latencies to search remained minimal at this time, but increased again at the other times, and were longest on day 13 at 1 h after nursing. Performance changes with time of day corresponded to daily changes in activity, and, after the first week, suggested a further development of underlying motivational mechanisms.
Abstract: By using the response of newborn pups to test for the presence of nipple-search pheromone on female rabbits, it could be shown that:
1. In non-breeding does pheromone emission follows a seasonal cycle with the peak in early summer, and this appears to be dependent on daylength.
2. At all times of year the probability of pheromone being present increases during pregnancy and decreases again during late lactation or following early removal of pups.
3. Pheromone emission is depressed following ovariectomy but can be stimulated by administration of estradiol.
Abstract: The suckling behaviour of domestic rabbit pups was studied by observation from below through a glass-bottomed nest box (3 litters), and stimuli relevant for nipple location were investigated experimentally by shaving and covering does' bellies in various ways (16 litters).
1. Rabbit pups are able to secure and suck nipples within seconds of their mother's arrival. They respond to the vibrational and tactile stimuli with rearing movements. Contacting the doe's fur, they push their muzzles into it and display probing and rapid lateral head movements characteristic of nipple search behaviour until a nipple is grasped.
2. Odour cues on the skin elicit and sustain nipple search behaviour, and appear to in- crease in strength toward nipples. High concentrations or, possibly, a second odour at nipple bases, release nipple grasping.
3. Because of the short ranging action of the odour, fur may help the pups to initiate and keep contact with the mother's ventrum, and to detect the odour gradient by stimulating lateral head movements. However, neither fur direction nor thermal gradients appear important for nipple location.
4. Of the 3-4 minute daily nursing time does took on average 5.2 secs to assume the nursing posture and pups a median time of 11.5 secs to contact the doe's belly fur, and a median of 6.0 secs to reach and secure a nipple. Unexpectedly, the pups released and switched nipples frequently, on average 2.6 times per minute, thus further reducing the total time spent on nipples. However, the efficiency of pups improved with age and the percentage of nursing time spent sucking increased from about 47To to 72% during the first 12 days.
5. The nipple search releasing odour of rabbit does may be considered as a true pheromone as the behaviour elicited is reliable and highly stereotyped.
Abstract: Domestic rabbit pups (22 litters of 6 pups each) were raised in plexiglass nest boxes, and their behaviour was studied under various experimental conditions during the first 14 days of life. 1. Rabbit pups show a stereotyped pattern of behaviour closely associated with the once daily nursing visit of the doe until they start to leave the nest on day 13. 2. One to two hours before nursing pups group tightly together and become exposed from the nest material. In young litters these behaviours appear to improve access to the doe's belly and to shorten the time the doe spends in the nest. 3. Rabbit pups are unusual in that they display a vigorous burst of post-nursing activity, i.e. simultaneous urination followed by digging and burrowing around the nest. This activity is triggered by the nursing act and appears to contribute to thermoregulatory efficiency as an insulating cover is quickly regained. 4. Within about 30 minutes pups reaggregate and remain well covered until the next nursing time. 5. The anticipatory uncovering appears to represent a circadian rhythm, and not to be simply due to hunger, as demonstrated in isolated litters deprived of one nursing. 6. Presumably the less time wild does spend in the nursery burrow the less chance there is of predators trapping them or finding the young. The ability of the pups to anticipate the nursing and the their thermoregulatory self-sufficiency may contribute to shortening the time rabbit does must spend in the nest.
Abstract: Discussions of adjunctive behavior still largely refer to polydipsia induced by food delivery schedules to food deprived animals. In the present experiment polydipsia was induced when socially isolated monkeys housed in barren home cages were exposed to scheduled deliveries of film and scheduled viewing of other monkeys. Thes data suggest the greater generality and complexity of adjunctive behaviors and show that schedule-induced polydipsia cannot be regarded as an artifact of food associated drinking.
Abstract: All mammalian young depend for their survival for at least some period on the motherâs milk. Locating the mammary region, attaching to a nipple or teat, and being motivated to suck until milk flows is one of the first and most vital chal- lenges they face. For altricial species such as the European rabbit (Oryctolagus cuniculus), the cat (Felis silvestris catus) and the dog (Canis lupus familiaris) born without vision, not directly aided by the mother, and having to compete with litter- mates, the challenge is particularly great. All three species use chemical cues appar- ently emitted under hormonal control by lactating females to achieve this. From birth they quickly orient to the motherâs ventrum, rapidly locate nipples, and respond with nipple-search behavior and nipple attachment to other lactating females but not to non-lactating females. Kittens, but not rabbits or puppies, also quickly establish a nipple order in which each kitten uses primarily one or sometimes two particular nipples. Recognition of own nipples appears to depend on learned olfactory cues, possibly contained in each kittenâs own saliva. These three species illustrate simi- larities and differences in the use of chemical cues by mammalian young in the suckling context and raise questions warranting further investigation: are there com- monalities in the origin and chemical composition of the suckling signals emitted by the mothers of such taxonomically different species? Are there commonalities in the neural processing of such signals, for example, in the participation of the main and accessory olfactory systems? To what extent are inborn responses augmented or even replaced by learned chemical cues? And does the early experience of such cues affect the response to chemical signals in later life?
Abstract: Mexico City air pollution is associated with impaired olfactory function. Different aspects of odor perception are altered to varying degrees, olfactory sensitivity being the most affected. This is shown by the higher detection thresholds both for monomolecular substances and complex mixtures common in everyday life observed for Mexico City subjects compared to subjects from cleaner-air environments, but equally good performance in describing and naming odor stimuli. Also, air pollution seems to be related to an impaired ability in assessing food edibility. The adverse effects of air pollution on olfactory function appear to result mainly from peripheral damage to this system rather than from effects on more central, cognitive processes. This is supported by an extensive literature reporting the harmful effects of airborne contaminants on the nasal cavity, including to the respiratory and olfactory epithelia. People from air-polluted areas also showed poorer performance in a test of intranasal trigeminal function, which mediates the sensations of freshness, spiciness and pungency via free nerve endings that innervate the nasal cavity, and warns of the presence of potentially dangerous substances in the environment. Important topics for future research include how early in life such impairments are manifested, how they relate to different life circumstances, when and under what conditions they might be reversible, and of particular importance, to what extent they are related to the appearance of neurodegenerative diseases in the increasingly aging populations characteristic of many large urban areas.
Abstract: Efforts to understand the generation and maintenance of circadian rhythms have traditionally focused on the role of photic stimuli, and particularly on the influence of the daily light-dark cycle. However, recurrent non-photic events such as daily patterns in the availability of food can also regulate circadian systems and via mechanisms different to photic cues. A notable example is provided by newborn altricial mammals which, born blind and often in subterranean nests, cannot use photic cues to synchronize physiological and behavioral processes with relevant environmental events such as the nursing visits of their mother. Here we briefly review information on the development of circadian rhythmicity in newborn, nonvisual mammals, ending with a more detailed description of research in the newborn rabbit. Rabbit pups are born blind, spend their early life in a dark nursery burrow, and are only visited by their mother once every 24 hours for 3-4 minutes to be nursed. They anticipate this vital daily event with an increase in arousal and body temperature, both of which represent endogenously generated circadian rhythms entrained by nursing. In on-going work exploiting this unusually favorable mother-young system, we have found that rabbit pups show endogenous circadian patterns in the expression of clock genes in the hypothalamus similar to those reported in adult mammals, and that non-photic stimuli accompanying nursing such as maternal pheromonal cues can entrain the pupsâ various circadian functions. We conclude that the rabbit provides an unusually good opportunity to investigate the participation of non-photic cues in the development of the mammalian circadian system.
Abstract: The European rabbit, Oryctolagus cuniculus, in its domesticated form, is an important animal in biomedical research and in a number of countries is of economic significance for the production of meat and fur. In the wild, it is an appreciated game species, and in several countries it is also a major agricultural pest. The rabbitâs long association with humans has resulted in a large body of information on its general biology and it is now one of the most studied mammals in the wild. In whatever context, however, the rabbit is best known for its remarkable reproductive capacity. This is due in large part to the reproductive efficiency of the female (Fig. 1), a notable feature of which is the brief time mothers spend each day even with their newborn young (reviewed in Hudson and Distel 1982; 1989). After giving birth to the altricial young in a separate nursery burrow or in a chamber in the colony warren, the doe leaves, closes the entrance, and only returns to nurse for a few minutes once approximately every 24 h. As for several other lagomorphs (see below), such limited contact between mother and young is thought to have evolved to reduce the possibility of predators locating the nest from the attendance of the more conspicuous mother (Zarrow et al. 1965).
Abstract: Among mammals, rabbits (Oryctolagus cuniculus) show unusually limited maternal care and only nurse for a few minutes once each day. Successful suckling depends on pheromonal cues on the motherâs ventrum, which release a stereotyped and distinctive pattern of nipple-search behaviour in the young, and which have been termed the nipple-search pheromone. The present report summarizes what is currently known about this unusually effective chemical signal and compares this with information in more recent reports of a rabbit mammary pheromone thought to achieve the same function. We draw attention to anomalies in the present state of knowledge regarding the nature and action of these two sets of chemical signals, and thus to the continuing uncertainty as to the chemical nature and source of the cues governing nipple-search behaviour, and thus successful suckling, in the newborn rabbit.
Abstract: Ethical behavior is now a major issue in biomedical research, whether concerning the appropriate use of human or animal subjects, or integrity in the management of data and relations among students or colleagues. The authors of this chapter are members of the Commission in Bioethics, created by the Internal Council of the Institute of Biomedical research of the National University of Mexico, to formulate and implement a comprehensive code of ethical conduct among staff and students. As part of this effort, the present chapter is intended to promote awareness and discussion of this complex issue as a first step towards the construction of a system of values guiding the future development of medical and biomedical research in Mexico. Topics include: a) Research using human subjects; a brief history, present day ethical principles and guidelines, the nature of present day research, and the composition and function of committees overseeing this. b) Similarly, for research using animal subjects; a brief history, current use at the UNAM, and preset day ethical principles and guidelines. c) Scientific integrity, including the appropriate generation and treatment of data, and appropriate behavior towards colleagues and peers. d) The necessity for educational programs, and e) the recognition and acceptance of shared responsibility among institutional authorities, researchers, and students in ensuring ethical conduct, supported by the formulation and dissemination of a comprehensive and workable code of such conduct in biomedical research.
Abstract: An increasing number of studies suggest that learning plays a significant part in odor perception. Here we report the results of four studies which illustrate this point. In the first study we presented to 23 subjects with 40 everyday substances and by analysing the images and associations generated found that everyday odors are more precisely represented than might be inferred from naming ability alone. Secondly, we investigated the ability to discriminate between everyday odors by presenting three sets of six chemically and semantically related substances to 24 subjects and found a general correlation between familiarity, verbal identification and discrimination ability. However, the pattern of performance appeared quite idiosyncratic and, at least in part, to be due to individual differences in experience with some odorants. Thirdly, to investigate the degree of experience-dependent differences in odor perception, we presented 40 Japanese and 44 German women with 18 odorants - six thought to be typically Japanese, six to be typically European, and six to be international - and asked subjects to rate the intensity, pleasantness, familiarity and edibility of the odorants, and to name them and/or to describe associations evoked by them. Significant differences were found between the two populations on all measures, with the results suggesting differences in hedonic evaluation to be strongly influenced by culture-specific eating habits. Finally, to examine the relationship between familiarity, affect and intensity more closely, the sample was extended to include 40 Mexican women. We found, independent of differences in rating particular odors, positive correlations in all three cultures between familiarity and intensity, and between strength of affective judgement and intensity. Thus, even such a basic aspect of odor perception as intensity may be influenced by experience.
Abstract: Der Begriff "Prägung" wird in diesem Artikel für Lernformen benutzt, die einem natürlichem Kontext entstammen und durch eine sensitive Phase während eines bestimmten Entwicklungsstadiums bzw. physiologischen Zustandes gekennzeichnet sind. Obwohl Geruchsprägung in ganz unter¬schiedlichen Altersstufen vorkommt und bei adulten Tieren sogar besonders gut untersucht ist, stellen neue Befunde zum pränatalen Geruchslernen eine besondere Herausforderung für unser Verständis von Prägungsvorgängen dar. Es ist zum Beispiel die Frage, ob das pränatale Lernen auf anderen Mechanismen als das assoziative Lernen beruht und ob es sich um eine Art inzidentellen Lernens handelt? Auch ist unklar, wie die Geruchsinformation während der perinatalen Periode langfristig gespeichert wird, da sich während der Entwicklung die Zahl der neuralen Elemente des olfaktorischen Systems verändert bzw. ständig zunimmt.
Abstract: The remarkable reproductive efficiency of the European rabbit has long be recognized by biologists, agriculturalists, and hobby breeders alike. In considering the contribution of the doe to this success the present review emphasizes the important part played by the precise endocrine regulation of the tight sequence of reproductive behaviors. This is evident at at least three levels of temporal organization: 1) Time of year. Here the doe's extreme sensitivity to seasonal changes in photoperiod and ability to translate these into hormonal signals is of importance both in understanding the reproductive biology of wild populations and in designing optimal breeding programs for domestic stock. 2) The reproductive cycle. Here the precise hormonal regulation of the tightly organized behavioral sequence of mating, nest building, parturition, postpartum estrus, nursing and weaning is particularly evident. 3) Time of day. Finally, the contribution of circadian mechanisms is considered, with particular emphasis given to the day/night separation of nursing and parturition, and to the endocrinological significance of this.
Abstract: Among mammals, rabbits show unusually limited maternal care and only nurse for a few minutes once each day. Successful suckling is ensured by pheromonal cues on the doe's ventrum which release a stereotyped and distinctive pattern of nipple-search behavior in the young. The present report summarizes what is currently known about this unusually effective chemical signal with respect to the following topics: Its functional significance in the reproductive life of the rabbit; the behavioral response of the pups including the question whether they might acquire knowledge of such cues prenatally; olfactory processing including the finding that the behavioral response is mediated by the main rather than by the accessory olfactory system; hormonal control including a description of the estrogen-progesterone-prolactin cascade regulating changes in emission during the reproductive cycle; and finally, a description of a behavioral bioassay which it is hoped will eventually enable the chemical characterization of the pheromone.
Abstract: The unusually limited nature of maternal care in the rabbit, coupled with observations of foraging behavior in the wild, raises the question whether doe rabbits can transfer information about their diet to their offspring or otherwise assist them in making the transition to independent feeding. In aseries of studies using domestic rabbits, it was shown that the development of ingestive behavior constitutes a well-defined sequence of stages, the length of which depends on the reproductive condition of the doe. Further, by feeding does either aromatic juniper berries or thyme, which form part of the diet of a wild rabbit population currently under study, it was demonstrated that the motherâs diet during gestation and lactation influenced the food choice of pups at weaning, ant that this information ca be transmitted to the young either during nursing, via the fecal pellets deposited in the nest, or even prenatally.
Abstract: The self-injection of enkephalin and heroin by free feeding rats without a a food delivery schedule and by rats at 80% body weight on a FT-1 min food delivery schedule was investigated.
Results:
1. Rats can be induced to self-inject enkephalin centrally.
2. Environmental factors of reduced body weight and presence of a food delivery schedule are effective in establishing self-injection of enkephalin.
3. Th pattern of acquisition for the self-administration of enkephalin is similar to the heroin pattern.
DOI 
