Effects of neonatal estrogen treatment of female guinea pigs on mounting behavior in adulthood.

Female guinea pigs were treated with 200 micrograms estradiol dipropionate (ED) daily from Days 1 to 15 of life. As adults they all ovulated. After gonadectomy and estrogen-progesterone treatment in adulthood, lordosis behavior was evident and showed no decrements (compared with neonatally oil-treated controls) except for a marginal decrease in maximum duration scores. However, testosterone propionate treatment in adulthood significantly increased mounting behavior in neonatally ED-treated females compared to the controls. On the other hand, estrogen-progesterone treatment in adulthood stimulated mounting in the neonatally oil-treated group, but not in the neonatally estrogenized group. The results suggest that at least some aspects of steroid-dependent behaviors can be permanently influenced by estrogen treatment after the presumed prenatal critical period for sexual differentiation has been completed in guinea pigs.