Evidence for the Release of Ovulating Hormone in PMS-Treated Immature Rats ∗

Abstract

Summary

The ovulation inducing potential of anterior pituitary glands of immature rats induced to precocious puberty with PMS was assayed by a method employing ovulation in other (recipient) immature rats as the end point. Although timed injection of phenobarbital (PB) demonstrated the existence of a 1:30—4:30 p.m. critical period for ovulation in the donor rats, the pituitaries of these rats failed to exhibit a definitive decrease in ovulating hormone (OH) content by the end of the critical period. If the pituitaries were not removed until the day after the critical period, pituitaries from rats injected with saline at 1:30 p.m. on the day of the critical period contained significantly less OH than rats injected at this same time or at 4:30 p.m. with PB. The results of these experiments are interpreted to mean that though sufficient OH is released during the critical period to induce ovulation, OH release normally extends after the critical period; whenever administered, PB blocks subsequent release of pituitary OH.