Plasma noradrenaline and dopamine-beta-hydroxylase during sexual activity

Plasma noradrenaline (NA) concentrations and the activity of its synthetic enzyme, dopamine-beta-hydroxylase (DBH), were determined during sexual activity in one male subject on three occasions. Blood was obtained through an intravenous catheter by means of a peristaltic pump and an automatic fraction collector. NA was significantly (P less than 0.001) related to stages of sexual arousal and erection quality. Maximal arousal and erection was accompanied by plasma NA concentration 100% to 1200% higher than basal levels. NA levels also increased significantly with upright posture and with emotional stress. DBH activity did not correlate closely with sexual arousal and erection.