The maternal pheromone of the rat as an innate stimulus for pre-weanling young

An ephemeral pheromone of female house mice: perception via the main and accessory olfactory systems

Two experiments examined the chemosensory modalities by which males detect an ephemeral sex pheromone in the freshly voided urine of female mice. Experiment 1 examined the interaction of deafferenting the accessory olfactory system (vomeronasal organ removal) and subsequent sexual experience upon ultrasonic vocalizations by male mice to freshly voided female urine. In general, sexually experienced males vocalized substantially more than sexually naive males. In addition, males possessing a vomeronasal organ vocalized slightly more than those without. Nonetheless, a functioning vomeronasal organ clearly was not essential for vocalizing to fresh female urine. Experiment 2 examined the effects of deafferenting the main olfactory system (ZnSO4 nasal irrigation) and/or the accessory olfactory system (vomeronasal removal) in sexually experienced males. Males with both olfactory systems functioning vocalized at high levels to fresh urine, while males with only one functioning system vocalized at intermediate levels. Males with neither system functioning did not vocalize at all to fresh urine. In contrast, when female mice themselves served as stimuli, all groups of males vocalized at high levels. We conclude that adult male mice can detect the ephemeral pheromone via either the main olfactory system or the accessory olfactory system. However, vocalizations to the female herself can be mediated by other sensory systems as well.

An ephemeral sex pheromone in the urine of female house mice (Mus domesticus)

From previous research, the ultrasonic vocalizations of male mice (Mus domesticus) to female mouse urine were hypothesized to be learned as a result of classical conditioning during adult heterosexual encounters. According to this interpretation, a previously neutral conditioned stimulus in female urine comes to elicit vocalizations as a result of its association with some other unknown unconditioned stimulus associated with adult females. However, the research from which this hypothesis was derived utilized urine collected from females housed in metabolic cages. Three experiments further examined the classical conditioning hypothesis using two types of female urine: (i) metabolic-cage-collected urine and (ii) freshly voided urine. Experiment 1 demonstrated that, in contrast to vocalizations to metabolic-cage-collected urine, adult heterosexual experience was not necessary for males to vocalize to freshly voided female urine. In addition, unlike metabolic-cage-collected urine (Experiment 3), freshly voided urine remained a potent stimulus for eliciting vocalizations during repeated testing (Experiments 2 and 3). Finally, freshly voided urine appeared to cause a previously neutral stimulus (cotton swab) to acquire ultrasound eliciting properties (Experiment 2). We suggest from these findings that two chemosignals that elicit vocalizations from males may exist in female mouse urine: (i) a potent, but volatile or easily degraded, unconditioned stimulus to which males vocalize without sexual experience and (ii) a nonvolatile, chemically stable conditioned stimulus.

Prolonged responsiveness to the maternal pheromone in the postweanling rat

When rat young reach 27 days of age they stop responding to a pheromone carried in the feces of the lactating female. Because the consumption of such feces promotes the deposition of brain myelin, we suggested that response to the pheromone might continue as long as the amount of myelin per gram brain remained below adult levels. Our data support the suggestion. Pups deficient in myelin responded to the pheromone after 27 days of age.

Home odor preferences in young hares (Lepus capensis syriacus): effects of age and role of maternal presence

The odor preferences of mother-reared and hand-reared young hares between 1-30 days of age were studied. Subjects were exposed daily to three choice tests in which the following pairs of odors were presented: home cage odor (HCO)-neutral odor (NO); HCO-strange cage odor (SCO); SCO-NO. All young strongly preferred their HCO over SCO throughout the 30-day period. HCO was preferred over NO until the age of 20 days, while avoidance of SCO was shown during the first 10 or 20 days. The same experiment conducted on postweaned hares (31-50 days of age) revealed a strong preference for SCO over both HCO and NO. These findings may be interpreted with respect to the natural history of the hare and its unusual mother-young relationship, which, in the wild, is limited to a single daily meeting for nursing. It is suggested that the highly precocial hare recognizes and prefers its home odor independently of any maternal contribution to that odor, possibly relying on odor cues from its own body to return to its nursing site. Other possible advantages of these olfactory preferences, including predation avoidance and facilitation of social relationships, are discussed.

The maternal pheromone and deoxycholic acid in relation to brain myelin in the preweanling rat

We examined the lipid composition of blood and myelin in preweanling rats denied access to maternal feces. Levels of triglycerides and free fatty acids in the blood were reduced and in the brain the amount of myelin and the phospholipid concentration in myelin were also reduced. The addition of deoxycholic acid to ordinary laboratory chow prevented these deficiencies. We conclude that response to the maternal pheromone and the subsequent ingestion of deoxycholic acid through maternal feces promotes the deposition of normal brain myelin.

Dietary influences in the preferences of pre-weanling Long-Evans rats for the anal excreta of adult males

Male rats which ingest feces of lactating females produce anal excreta which is attractive to pups. This excreta is as attractive as that of lactating females and more attractive than the excreta of males eating a diet of lab chow only. Anal excreta of males which consume feces of lactating females is more attractive to pups than excreta of males that consume feces of nonlactating females. These results suggest that group or colony odors may develop from rats eating feces of other colony members and that infant rats may be more attracted to adults that have an odor which is similar to the maternal odor than adults which have different odors.