Effects on Lactation of Progesterone Injections Administered During Late Pregnancy in the Rat 1

Abstract

Summary

Progesterone injections administered during late pregnancy effectively inhibit lactation in the rat. Subcutaneous doses of 0.5 and 2 mg of progesterone in sesame oil twice daily between days 18 and 23 of gestation produced a greater inhibitory effect than 0.1 mg of progesterone similarly administered, particularly with regard to mortality and weight changes of the young, and the release of milk in nursing tests. The primary inhibition appears to rest on processes of milk ejection rather than milk secretion or the motivation to nurse.