Influence of the Hypophysis on Pregnant Mare's Serum Gonadotrophin-Induced Ovulation in Immature Rats

Summary. The injection of 30 i.u. pmsg in 27-day-old rats produced an ovulatory response which began after 24 to 36 hr and reached a maximum 72 hr after gonadotrophin treatment. There were two increments in the number of ova within this period: between 36 and 48 hr and between 60 and 72 hr. The results of timed experiments involving chlorpromazine blockade or hypophysectomy suggest that the first increment in the number of ova is independent of the pituitary gland but influenced by it. The latter increase seems to be pituitary-dependent since both procedures suppressed it.