Prenatal and neonatal androgen exposure interact to affect sexual differentiation in female rats

Rats were injected with oil on Days 17.5 and 18.5 of pregnancy or with 2 mg of testosterone propionate (TP) on Days 15.5 and 16.5, or Days 17.5 and 18.5, or Days 19.5 and 20.5. The female offspring were given oil or 5 micrograms of TP on Day 25 postconception. Among females exposed to TP only during prenatal ontogeny, a lower proportion of those treated on Days 17.5-18.5 of gestation displayed lordotic behavior than did the control group. Postnatal TP alone did not affect lordosis. However, all groups receiving combined pre- and postnatal TP showed impaired estrous patterns. The development of several components of morphology also was differentially affected by the timing of the androgen exposure. The data suggest that the differentiation of sexual behavior and reproductive morphology in the rat are influenced by an interaction of androgen dependent processes operating at different stages of perinatal ontogeny. Further, there may be an optimal fetal period during which androgenization sensitizes animals to low levels of testosterone circulating during neonatal development.