Abstract
Sexually mature Long-Evans male rats show a strict preference for odors of receptive females over those of males or ovariectomized females. Our previous study demonstrated that castration induces transient reversal of sex orientation (preferring males to females), which is diminished during the course of observation over a 3-week period (Xiao et al., 2003). In this study, we investigated the effects of testosterone (T), or dihydrotestosterone (DHT) on sex-orientation in castrated males using cholesterol (C) as control. Another group in which intact males were treated with an aromatase inhibitor, formestane (4-hydroxyandrostenedione, 4-OHA). Subcutaneous implantation of Silastic capsule containing T, DHT and 4-OHA, but not C, produced obvious male-typical orientation along with male sexual behavior. Males with T also preferred castrated males to sexually active males, whereas males with DHT or 4-OHA had no preference for castrated males. After the removal of the capsule or castration of 4-OHA males, T males showed transient reversal of sex orientation for 2-3 weeks, even though they showed male sexual behavior when placed with receptive females. In contrast, DHT and 4-OHA males had no preference at all after the removal of the capsule or castration. The results indicate that estrogen generated by aromatization of testosterone induces female-like sex orientation in the castrated males. [Jpn J Physiol 55 Suppl:S213 (2005)]
