9421759 Roselli Gonadal steroids have profound sex-specific effects on reproductive function and behavior. For instance, testosterone, which stimulates a repertoire of masculine sexual behaviors in males, is much less effective in eliciting these behaviors in females. This sex difference in androgen responsiveness is established during early life and is believed to be related to sex differences in brain structure as well as the concentrations of neural androgen receptors. Less attention has been paid to the possible contribution of sex differences in neural androgen metabolism. Aromatization of testosterone to estradiol by the brain is required to activate male copulatory behaviors. The levels of aromatase activity are sexually dimorphic in medial preoptic area of the brain which is essential for the display of male sexual behaviors. Dr. Roselli proposes a model to explain the role of aromatization in the development of sex difference in behavior. The model predicts that the aromatization pathway of androgen metabolism is more active in the male than in the female brain because of increased capacity to up-regulate aromatase activity. Thus, when adult males and females are given identical stimulation with testosterone, more estrogen is produced in the male medial preoptic region which contributes the greater behavioral response in males. Dr. Roselli will investigate whether perinatal androgen exposure increases aromatase activity and androgen receptor binding in the brain of females, establish whether testosterone increases neural estrogen receptor binding more in males than females, determine if androgens increase brain aromatase synthesis and activity more in males than females, and examine if estradiol stimulates male behavior in females to the same level as males treated with testosterone alone. The proposed studies have the potential to further our understanding of brain-related sex differences in behavior in mammals, including man.
