Sexual impotence is associated with a reduced production of oxytocin and with an increased production of opioid peptides in the paraventricular nucleus of male rats.

Oxytocin plays a physiological stimulatory role on sexual behavior. Conversely, opioid neuropeptides play a physiological inhibitory role. Here we show that in sexually impotent rats there is a reduced expression of oxytocin mRNA and an increased expression of proenkephalin and pro-dynorphin mRNA in the paraventricular nucleus of hypothalamus (PVN), a brain structure of key importance for sexual behavior. These data suggest that an imbalance in the production of oxytocin and of opioid peptides in the PVN, with prevalence of opioid peptides, may underlie a condition of sexual impotence.