OXY binds to membrane receptors. Action is not mediated by cAMP. 1. Stimulates IP 3 production. PGF 2 a stimulates contraction of uterine smooth muscle. Uterus becomes progressively more sensitive to OXY as pregnancy progresses.
Progesterone inhibits uterine contractility.
B. Milk ejection . Does not stimulate milk production. Milk ejection reflex. Milk ejection occurs within 10-12 seconds of stimulation. Evolution of the Neurohypophysial Hormones.