Testosterone-induced brain aromatase is sexually dimorphic.

Female quail are less sensitive than males to the activating effects of testosterone (T) on behavior. Testosterone induces hypothalamic aromatase activity more efficiently in males than in females (higher Vmax but similar Km). As the conversion of T to estradiol (E2) is important for the activation of male sexual behavior, we propose that the incapacity of the female hypothalamus to produce behaviorally active E2 contributes to their insensitivity to T. The 5 alpha-reductase, which converts T into 5 alpha-dihydrotestosterone (5 alpha-DHT), is induced by T specifically in the anterior hypothalamus of both sexes.