Neonatal androgen affects copulatory behavior in the female musk shrew

The role of neonatal testosterone in the development of copulatory behavior was examined in an insectivore, the musk shrew (Suncus murinus). Female mu sk shrews were treated with testosterone propionate (TP) for the first 5 da ys of life and then tested in adulthood for either female or male-like copu latory behavior. Early TP had a masculinizing effect; neonatally treated an imals mounted a stimulus female more frequently, and with shorter latencies , in response to adult testosterone treatment than did control females. Neo natally androgenized females also showed deficits in female sexual behavior ; few received ejaculations from stud males. This difference was likely cau sed by increased aggression exhibited by the neonatally TP-treated females toward males. In turn, female aggression decreased efficiency of male partn ers' intromission attempts. Early TP treatments also caused structural abno rmalities in the ovaries, but did not effect their capacity to ovulate in r esponse to either gonadotropin-releasing hormone or human chorionic gonadot ropin injection. In sum, exposure to TP during development augmented displa y of male-like behavior in females and had subtle deleterious effects on ex pression of feminine behavior. (C) 1998 Academic Press.