SEXUAL-DIFFERENTIATION OF ODOR AND PARTNER PREFERENCE IN THE RAT

Previous studies have shown that adult male rats, in which brain estro gen formation was inhibited neonatally by SC administration of the aro matase inhibitor 1,4,6-androstatriene-3,17-dione (ATD), show an altere d sexual partner preference. When tested in a three-compartment box, s uch gonadally intact ATD males approach and mate both with the estrous female and the sexually active male, whereas normal males prefer to a pproach and mate with the estrous female, avoiding the stimulus male. After castration in adulthood and estradiol treatment, ATD males prefe r sexually active males. Similarly treated normal males prefer estrous females, and estrous females prefer to mate with males. Fn the presen t study, we asked what stimulus characteristics of active males vs. es trous females determined the different sexual preferences of males, AT D males, and of females. Were they chemosensory cues or more distal cu es such as actually seeing and hearing the stimulus animals or the rew ard of sexual activity with the stimulus animals? Sex differences in p reference were evident when animals were given a choice between soiled bedding from estrous females and from sexually active males. ATD and control males spent significantly more time on soiled bedding from est rous females than on soiled bedding from sexually active males. Contro l females spent significantly more time on soiled bedding from sexuall y active males than on soiled bedding from estrous females. More dista l cues, such as seeing and hearing the stimulus animals, revealed diff erences in preference between control males and females, but not betwe en ATD and control males. Physical interaction with the stimulus anima ls was a prerequisite for revealing differences in preference between ATD and control males. Then, the behavior of ATD males was clearly int ermediate between that of normal male and female rats. In conclusion, neonatal estradiol is important for the psychosexual development of th e male rat. However, the present data suggest that the psychosexual de velopment of the male rat also requires either prenatal estradiol or p erinatal testosterone.