(163) IS THE ENDOGENOUS VASOACTIVE PEPTIDE OXYTOCIN A PHYSIOLOGICAL MEDIATOR OF PENILE ERECTION IN THE ADULT MALE?

It is has been established that the pro-erectile effects of the activation of dopaminergic receptors (D1/D2), for example, by the receptor agonist apomorphine, involves oxytocinergic pathways descending from the hypothalamus to spinal autonomic centers. Although it has been demonstrated that, in rats, the injection of oxytocin into the paraventricular nucleus or the hippocampus induced penile erection, the significance of the peptide in the control of sexual arousal and penile erection in men still is only poorly understood. The present study was undertaken to determine as to whether oxytocin (OT) plasma levels alter in the systemic and cavernous blood of healthy males under different conditions of sexual arousal, as exemplified by the penile conditions flaccidity, tumescence, rigidity and detumescence.

Twenty-five (25) healthy adult males were exposed to visual and tactile erotic stimuli in order to elicit penile tumescence and rigid erection. Blood was taken from the corpus cavernosum (CC) and a cubital vein (CV) at the penile conditions flaccidity, tumescence, rigidity and detumescence. Following extraction from the plasma by applying an octadecasilyl silica matrix, oxytocin was measured by means of a radioimmunoassay (RIA).

An increase was observed in median OT plasma levels (given in pg/ml) in the systemic and cavernous blood when the flaccid penis became tumescent (CV: from 71 ± 41 to 79 ± 49.5, CC: from 66.7 ± 34 to 75 ± 44). From tumescence to rigidity, OT further rose in the cavernous blood (to 81 ± 58), whereas it remained unaltered in the systemic circulation. During detumescence, oxytocin plasma levels dropped in the cavernous blood but again increased in the systemic blood (to 94 ± 49).

Based on the results, it seems likely that there is a role of OT in the mechanism of male sexual arousal and penile erection.

The authors have no conflcts of interest to declare.