Androgen Metabolism in the Brain of the Green Anole Lizard (Anolis carolinensis)

Abstract

Activities of the steroid metabolizing enzymes aromatase and 5α-reductase have been documented in species ranging from fish to humans, yet relatively little work has been done in this area in reptiles. In the green anole lizard,Anolis carolinensis,steroid hormones are critical to the display of both masculine and feminine sexual behaviors. For example, dihydrotestosterone and testosterone can stimulate both masculine courtship and copulatory behaviors, and estrogen and testosterone facilitate feminine receptivity. These results suggest roles for both aromatase (which catalyzes the conversion of testosterone to estradiol) and 5α-reductase (which converts testosterone to dihydrotestosterone). This study documents the presence of both enzymes in the brain of the green anole and indicates that the activity of 5α-reductase is much higher than that of aromatase in whole brain homogenates. However, differences exist among brain regions, such that aromatase activity is higher in preoptic area/hypothalamic dissections, whereas 5α-reductase is much more active in the brain stem. These variations in regional enzyme activity may influence steroid hormone regulation of specific sexual behaviors in male and female anoles.