Steroid control of sexual behavior and brain aromatase in the dove: effects of nonaromatizable androgens, methyltrienolone (R1881), and 5 alpha-dihydrotestosterone

This study examines the effects of nonaromatizable androgens, methyltrienolone (R1881) and 5 alpha-dihydrotestosterone (DHT) on aggressive courtship and vocal behavior in the male ring dove. Since androgens may influence behavior by increasing the formation of estrogen in the brain, the effects of R1881 and DHT on brain aromatase activity were also studied using an in vitro microassay. Under conditions in which testosterone induced aggressive courtship patterns, the nonaromatizable androgens were ineffective. But DHT and R1881 induced vocal behavior with equal efficiency, indicating that androgens can influence mechanisms of vocal behavior without conversion to estrogens. The behavioral effectiveness of both hormones was reduced (approximately 50%) when the period between castration and treatment was doubled. Testosterone propionate increased formation of E2 from 3H-testosterone in both the preoptic (POA) and anterior hypothalamic areas. Neither of the nonaromatizable androgens affected POA aromatase activity. The results suggest that only the aromatizable androgen, testosterone, which is also required specifically for male courtship, increases preoptic formation of estrogen.