MILK-EJECTION ACTIVITY (OXYTOCIN) IN PERIPHERAL VENOUS BLOOD IN MAN DURING LACTATION AND IN ASSOCIATION WITH COITUS

Abstract

The direct estimation of oxytocin in blood during suckling in women has only been reported by two groups of workers, who obtained conflicting results. Hawker & Robertson (1957) and Hawker, Walmsley, Roberts, Blackshaw & Downes (1961) failed to detect a change in the oxytocin content of peripheral venous blood during suckling. However, Coch, Fielitz, Brovetto, Cabot, Coda & Fraga (1968) demonstrated the presence of oxytocin (12–25 μu./ml. plasma) in internal jugular venous blood collected from women during suckling. The present study investigates the possible release of oxytocin during suckling and coitus in man by direct estimation of the hormone in the blood. No previous estimation during human coitus has been reported, but in domestic animals an increase in the oxytocin content of the blood has been claimed after mating (Walmsley, 1963) and after artificial stimulation of the genitalia (Fitzpatrick, 1957; Roberts & Share, 1968). Three suckling experiments, with the same