An Inhibitory Effect of Oxytocin on the Milk-Ejection Reflex

Residual milk, that milk not ejected from mammary alveoli of lactating dairy cows at the completion of normal milking, was collected immediately after the intravenous injection of 10 USP U oxytocin. Cows given 100 USP U oxytocin subcutaneously 8–9 hr before milking had significantly more residual milk thansaline-injected controls. This effect was not altered when 8 mg epinephrine was administered at the time of oxytocin treatment. Some possible mechanisms and implications of these observations have been discussed. (Endocrinology 82: 179, 1968)