抄録
In the rat, receptive females are attracted by sexually active males, whereas matured males approach estrous females. In order to explore the neuroendocrine mechanisms of such odor-based preferences, we established a 3-compartment apparatus and demonstrated clear sexual dimorphism. Furthermore, castrated male rats implanted with Silastic capsules containing testosterone (T), dihydrotestosterone (DHT) or estradiol benzoate (EB), and gonadally intact males with aromatase inhibitor all showed normal, male-typical preference pattern. Removal of the T and EB capsules induced transient reversal of their sexual orientation, that is, those males spent longer time to explore odor of sexually active males to that of receptive females or castrated males. This phenomenon occurs for 2–3 weeks after orchidectormy, and female rats never show the reversal after removal of sex steroids. The results suggest that in male rats, a high level of estrogen provokes male-type preference, and a residual low level of estrogen 2 weeks after castration elicits female-type preference. We also investigated the effect of lesions in the medial amygdala and the preoptic area on odor preference of male rats. Medial amygdala lesions disrupted preference for castrated male odor to sexual active male odor, but did not affect preference for receptive female odor, while medial preoptic lesions eliminated all of the preferences. In a point of view of the chemosensory processing system, the MeA is located in the upstream of the POA. Nevertheless, POA lesions had broader influences on preference, suggesting the circuit processing preference for estrous odor that bypassed the MeA. [J Physiol Sci. 2008;58 Suppl:S34]
