RELATION BETWEEN THE SECRETION OF FSH DURING THE PERIOVULATORY PERIOD AND OVULATION DURING THE NEXT CYCLE

A dose-dependent reduction in the secretion of FSH during estrus in the hamster was induced by the injection of increasing volumes of bovine follicular fluid (bFF). Partial inhibition of the release of FSH during estrus was observed after 120 μl of bFF was administered to hamsters at 3 h intervals beginning at 1800 h during proestrus and continuing until 0900 h during estrus. Four days later, significantly fewer ova were ovulated by these animals (P<0.01) than by controls. Complete inhibition of the release of FSH at estrus was observed when the volume of bFF was 500 μl/injection. In this group, an even greater reduction occurred in the number of ova recorded 4 days later. To reduce the amount of FSH released during proestrus and abolish the estrous FSH release, 500 μl of bFF/injection was administered at 3 h intervals beginning at 0900 h during proestrus in another group and continuing until 0900 h during estrus. During the next periovulatory period, a proestrous elevation in estradiol and gonadotropins was not observed and ovulation did not occur during estrus in 9 of 10 animals. These results suggest that the proestrous and estrous releases of FSH play an important role in the initiation and maintenance of ovarian cyclicity in the hamster. In addition, the number of ova ovulated during the next cycle is proportional to the release of FSH during the periovulatory period.