Changes in oxytocin and vasopressin secretion during sexual activity in men.

We measured plasma oxytocin (OT) and arginine vasopressin (AVP) concentrations in 13 normal men during sexual arousal and ejaculation. Mean plasma AVP increased from 1.4 +/- 0.2 (+/- SE) to 5.3 +/- 1.7 pmol/L (P less than 0.05) during arousal, but there was no significant change in OT. In contrast, at ejaculation mean plasma OT rose from a basal value of 1.4 +/- 0.3 to 7.3 +/- 0.6 pmol/L (P less than 0.01) and then fell to basal concentrations in 30 min. AVP, however, had returned to basal levels at the time of ejaculation and remained stable thereafter. We conclude that in man AVP is secreted during sexual arousal, and there is, subsequently, a selective release of OT at the time of ejaculation.