SEXUAL-DIFFERENTIATION OF SEXUAL-BEHAVIOR AND PREOVULATORY LH SURGE IN EWES

Adult ewes were studied after prenatal treatment with androgen. Although seven of the eight androgenized ewes (ANDR) when intact presented signs of cyclic ovarian activity at least once, none of them showed cyclic female receptivity when intact or after ovariectomy and progesterone (P) + estradiol (E2) treatments, whereas all ten control (CONT) ewes did. Receptivity also was induced in CONT, but not in ANDR, ewes by long term E2 or testosterone (T) treatments. Increases in LH levels, with latency and duration similar to the LH surges of the CONT ewes, were observed in six (P + low E2 cycle) and five (P + high E2 cycle) of the eight ANDR ewes. The maximum LH level was lower in the ANDR than in the CONT ewes after high E2 treatment (p < 0.002). Progesterone had a clear inhibitory effect on the induction of the LH surge by E2 only in the CONT ewes. Male-type mounting and nudging were observed more often in the ANDR than in the CONT ewes when intact (p < 0.05). However, there was no facilitation of male sexual behaviour induced by long term E2 or T treatment in the ANDR compared to the CONT ewes. Progesterone inhibited male behaviour induced by T in the CONT but not in the ANDR ewes. This study shows that prenatal androgens defeminze LH secretion and sexual behaviour of ewes in a dissociated manner. It also suggests that prenatal androgen does not really masculinize the females but decreases their sensitivity to the inhibitory effect of P, and thus extends the "juvenile state" in which male-like patterns appear independently of the hormone milieu.