Hormonal regulation of chemosignal-stimulated precopulatory behaviors in male housemice (Mus musculus).

Five experiments examined the hormonal regulation of the precopulatory reproductive behavior of male housemice of two genotypes (DBA/2J inbreds and C57BL/6J X AKR/J hybrids). The two precopulatory behaviors examined were preferences for female urinary odors and ultrasonic courtship vocalizations to anesthetized females. The preferences were then used to make inferences about odor attractiveness. Gonadally intact hybrid males were highly attracted to the airborne urinary odors of female mice but were either indifferent to, or exhibited less attraction to, male urinary odors. Castration decreased male attraction to female odor such that castrated males were equally attracted to male and female odors. Normal levels of attraction could be maintained in castrated hybrid males by Silastic implants of either testosterone or estradiol. While Silastic implants of dihydrotestosterone (DHT) were also effective in maintaining attraction in hybrids, this hormone was ineffective in inbreds. The effectiveness of estradiol, DHT, and testosterone in maintaining attraction following castration was paralleled in castrated hybrids by the effects of these hormones in maintaining courtship vocalizations to females. In contrast to the genotype-specific effects of DHT upon behavior, DHT was effective in both genotypes in maintaining seminal vesicle weight. Estradiol, on the other hand, which was quite effective in maintaining both precopulatory behaviors in hybrids, had little effect upon seminal vesicle weight. Thus these experiments dissociate the behavioral effects of steroids from their effects upon peripheral morphology. We suggest that testosterone can activate precopulatory behaviors following either aromatization or 5-alpha reduction but that genetic variability somehow gives rise to strain differences in DHT responsiveness.