PROLACTIN PRODUCTION AND LACTOGENESIS IN RATS AFTER OVARIECTOMY IN LATE PREGNANCY

Ovariectomy on day 17 of pregnancy in rats that normally give birth on day 23 induced lactogenesis and foetal resorption but did not alter the pattern of change in pituitary or plasma prolactin concentration. Plasma prolactin levels increased significantly in both ovariectomized and sham-operated animals from days 18-22 of pregnancy. This suggests that factors other than ovarian products control the rise in late pregnancy of plasma prolactin in the rat. The results support earlier reports that progesterone withdrawal may be the lactogenic trigger in the rat