Reinitiation of ovulatory cycles in pituitary stalk-sectioned rhesus monkeys: evidence for a specific hypothalamic message for the preovulatory release of luteinizing hormone.

Abstract

Female rhesus monkeys received intermittently infused GnRH after their pituitary stalks had been sectioned and either a Teflon or a Silastic barrier had been placed between the cut ends of the stalk. This mode of GnRH infusion (1 μg/ min for 6 min each hour) caused follicular development and an increase in serum 17β-estradiol (E2) levels to between 200–300 pg/ml, but did not result in ovulation in animals with Teflon barriers. Basal serum LH and FSH levels in these animals were comparable to those observed in intact cycling monkeys. In three animals with Silastic barriers (0.13 or 0.65 mm thick), the identical GnRH treatment resulted in follicular growth and ovulation. To determine if Silastic membranes could serve as a barrier against GnRH, we constructed Silastic capsules (wall thickness, 0.65 mm), filled them with GnRH, and implanted them sc into ovariectomized hamsters primed with E2. There was an increase (P < 0.05) in serum GnRH in animals treated with GnRH capsules, and serum LH was greater (P < 0....