Robyn Hudson

Pheromonal release of suckling in rabbits does not depend on the vomeronasal organ

Newborn rabbits are completely dependent on a pheromone present on the mothers 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.

Assessing pain threshold in the rat: Changes with estrus and time of day

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.

Nipple Location By Newborn Rabbits: Behavioural Evidence for Pheromonal Guidance

In einem mit Glasboden versehenen Nistkasten wurde das Saugverhalten neugeborener Hauskaninchen von unten beobachtet (3 Wurfe). Durch Experimente, in denen der Bauch der Hasin rasiert und in verschiedener Weise abgedeckt worden war, wurden die relevanten Reize fur das Auffinden der Zitzen untersucht (16 Wurfe). 1. Kaninchenjunge konnen bereits wenige Sekunden nach Ankunft der Mutter Zitzen finden und besaugen. Auf Vibrations- und Beruhrungsreize reagieren sie mit AufrichtBewegungen. Sobald sie mit dem Fell der Hasin in Kontakt kommen, stosen sie ihre Schnauzen tiefer und fuhren die fur Zitzensuchverhalten typischen, senkrechten (Proben) und seitlichen Kopfbewegungen aus, bis sie eine Zitze ergriffen haben. 2. Das Zitzensuchverhalten wird durch Geruchsstoffe der Haut ausgelost und aufrecht erhalten. Die Starke des Geruchs scheint in Richtung Zitzen zuzunehmen und besonders hohe Konzentrationen an der Zitzenbasis oder ein moglicher zweiter Geruch losen das Ergreifen der Zitzen aus. 3. Wegen der geringen Reichweite des Geruchs hilft wahrscheinlich das Fell der Mutter den Jungen Kontakt mit der Bauch aufzunehmen und zu bewahren, und durch Verstarkung der seitlichen Kopfbewegungen den Geruchsgradienten zu entdecken. Jedoch sind fur das Auffinden der Zitzen weder der Fellstrich noch Temperaturgradienten der Haut wichtig. 4. Von der gesamten Saugezeit, pro Tag 3-4 Minuten, benotigten die Hasinen im Mittel 5,2 sec, um die Saugehaltung einzunehmen, die Jungen 11,5 sec (Median), um das Bauchfell der Mutter zu erreichen und 6,0 sec (Median), zum Zitzen zu finden und zu ergreifen. Unerwartet war, das Kaninchenjunge haufig Zitzen loslassen und wechseln, im Mittel 2,5 mal pro Minute, wodurch sich die an Zitzen insgesamt verbrachte Zeit weiter reduzierte. Jedoch nahm mit dem Alter auch die Leistungsfahigkeit der Jungen zu und der relative Anteil der eigentlichen Saugezeit erhohte sich wahrend der ersten 12 Lebens-tage von circa 47% auf 72%. 5. Der Zitzensuchverhalten auslosende Geruch kann als ein Pheromon im eigentlichen Sinn angesehen werden, da ein stereotypes Verhalten reproduzierbar ausgelost wird.

The Pattern of Behaviour of Rabbit Pups in the Nest.

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 does 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.

From molecule to mind: the role of experience in shaping olfactory function.

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 theu2009sensory 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.

Discriminating parts from the whole: determinants of odor mixture perception in squirrel monkeys, Saimiri sciureus

AbstractIn 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:n 1.Discriminability generally decreased as the number of components in the submixture increased.2Submixtures 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.n 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.

The contribution of the olfactory and tactile modalities to the nipple-search behaviour of newborn rabbits

SummaryBy 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:1.Both the olfactory and tactile modalities are essential for the successful performance of nipple-search behaviour.2.While bilateral bulbectomy completely eliminates searching, and hence suckling, unilateral bulbectomy has relatively little effect.3.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.4.In contrast to unilateral bulbectomy, unilateral denervation of the muzzle results in a lateralization of head movements during searching, nipple grasping and nipple release.

Chin marking behavior, sexual receptivity, and pheromone emission in steroid-treated, ovariectomized rabbits

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).

Nipple-search pheromone in rabbits: dependence on season and reproductive state

SummaryBy 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.

Sensitivity of female rabbits to changes in photoperiod as measured by pheromone emission.

SummaryNewborn rabbits are completely dependent on a pheromone on the mothers 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.nPheromone emission would thus seem to provide a sensitive test of photoperiodic responsiveness in nonbreeding female rabbits, and a convenient, non-invasive indicator of their reproductive state.