Aromatase activity and regulation of sexual behaviors in the green anole lizard.

Sexual behaviors in green anoles are regulated by steroid hormones. Androgens activate the display of masculine courtship and copulatory behaviors, and estradiol activates feminine receptivity. Testosterone can also facilitate receptivity in females. The present study was conducted to test the role of converting testosterone to estradiol (aromatization) in the regulation of sexual and aggressive behaviors. Adult males and females were gonadectomized and implanted with a Silastic capsule containing either testosterone propionate (T) or estradiol benzoate (E) or with an empty (blank, BL) capsule. T- and BL-treated animals were then given injections of either Fadrozole (FAD, an aromatase inhibitor) or saline (SAL). E-treated animals received saline injections. Each individual was then tested alternately with male and female stimulus animals. Overall, T stimulated masculine sexual behaviors and receptivity, but the androgen had little effect on the display of aggressive behaviors. The inhibition of aromatase activity by treatment with Fadrozole eliminated the effect of T on receptivity. In contrast, Fadrozole treatment had no effect on mounting behavior or the frequency of courtship bouts. The inhibition of aromatase activity did increase the number of dewlap extensions (the display of a red throat fan) during courtship. These results suggest that the metabolism of testosterone to estradiol is a mechanism through which androgens can facilitate receptivity, and that such aromatization of testosterone is not required for the display of masculine sexual behaviors. In addition, females performed courtship and mounting behaviors less frequently than males, suggesting that an organizational component to steroid hormone regulation of sexual behaviors may exist in the anole.