Effects of prenatal testosterone and ATD on reproductive behavior in guinea pigs.

Most sexual dimorphisms in reproductive behavior are hormonally organized in the guinea pig. The study sought to determine whether the sexually dimorphic requirement for the aromatization of testosterone in the activation of mounting is organized by testosterone prenatally and whether aromatization of testosterone contributes to the organization of mounting behavior. Pregnant females were treated with testosterone, the aromatase inhibitor ATD, or vehicle from days 28-65 of gestation. The offspring were gonadectomized and tested as adults for lordosis and androgen-activated mounting behavior. Prenatal testosterone treatments altered the hormonal requirements for androgen-activated mounting in females such that they resembled normal males, and did not require aromatization as adults. Prenatal inhibition of aromatase activity decreased mounting activity in females but not in males. This treatment had no influence on lordosis in either sex. The results support the hypothesis that the same hormones that activate mounting behavior in the adult guinea pig are responsible for the organization of mounting behavior.