Spinal proerectile effect of oxytocin in anesthetized rats

The spinal cord contains the neural network that controls penile erection. This network is activated by information from peripheral and supraspinal or igin. We tested the hypothesis that oxytocin (OT), released at the lumbosac ral spinal cord level by descending projections from the paraventricular nu cleus, regulated penile erection. In anesthetized male rats, blood pressure and intracavernous pressure (ICP) were monitored. Intrathecal (it) injecti on of cumulative doses of OT and the selective OT agonist [Thr(4),Gly(7)]OT at the lumbosacral level elicited ICP rises whose number, amplitude, and a rea were dose dependent. Thirty nanograms of OT and one-hundred nanograms o f the agonist displayed the greatest proerectile effects. Single injections of OT also elicited ICP rises. Preliminary injection of a specific OT-rece ptor antagonist, hexamethonium, or bilateral pelvic nerve section impaired the effects of OT injected it. NaCl and vasopressin injected it at the lumb osacral level and OT injected it at the thoracolumbar level or intravenousl y had no effect on ICP. The results demonstrate that OT, acting at the lumb osacral spinal cord, elicits ICP rises in anesthetized rats. They suggest t hat OT, released on physiological activation of the PVN in a sexually relev ant context, is a potent activator of spinal proerectile neurons.