Naloxone inhibits oxytocin release at orgasm in man

We examined the effect of naloxone on plasma oxytocin levels during sexual activity in men. Eight normal men took part in a double-blind, two-period, cross-over design. Mean plasma oxytocin rose to 362% of baseline values at orgasm with placebo (saline) but showed no increase with naloxone (P less than 0.01). While naloxone had no effect on heart rate or blood pressure at orgasm, a decrease in the level of subjective arousal and pleasure at orgasm was noted. We conclude that opioid receptor blockade with naloxone has an inhibitory effect on the neural pathways mediating the oxytocin response at orgasm.