Prenatal androgen exposure, preoptic area and reproductive functions in the female rat

Pregnant rats were injected with 4 mg of testosterone propionate (TP) from days 15 to 22 of pregnancy or a single dose of 4 mg TP on day 17 or 21 of pregnancy. Female offspring treated with TP or the vehicle prenatally were sacrificed at 90 days of age. The volume of the cluster of intensely stained neurons in the medial preoptic area, the 'sexually dimorphic nucleus of the preoptic area' (SDN-POA), was found to be affected by prenatal exposure to TP. The effect of TP on the development of the SDN-POA was most remarkable in the animals treated with a single dose of Tp on day 17 of pregnancy, whereas TP injection on day 21 of pregnancy had no remarkable effect. These results suggest that continuous prenatal exposure to TP is not essential for stimulation of the development of the SDN-POA, suggesting the presence of a critical period during which the SDN-POA is most sensitive to the androgen. Although 4 out of 11 females exposed to TP from days 15 to 22 were sterile, the ovarian function of most of the TP-exposed offspring was normal. Furthermore, prenatally TP-exposed females failed to show behavioral masculinization and defeminization. All these females displayed high lordotic response levels and only rarely showed mounting behavior. These results suggest that the absolute volume of the SDN-POA does not seem to be directly correlated with the regulation of the cyclic release of gonadotropins and/or expression of sexual behavior.