Neurophysiological aspects of penile erection: the role of the sympathetic nervous system.

Recent studies have revealed that the initiation, maintenance and rigidity of penile erection are under parasympathetic and somatotopic control. The mechanism of penile detumescence is still under debate. Single and combined cavernous and hypogastric nerve stimulation was used to study the influence of the sympathetic nervous system on penile erection and to identify the mechanism of penile detumescence. Penile arterial flow and intracorporeal pressure recordings during various stimulation patterns indicated that erection induced by stimulation of the cavernous nerve could be blocked by excitation of the upper hypogastric nerves. Venous outflow studies demonstrated that the inhibitory effect of the sympathetic nervous system was due to active vaso- and corporeal smooth muscle constriction. It was concluded that subsidence and suppression of erection is a sympathetic function. Previous studies have shown that the neurophysiology of erection can be explained by 3 major inhibitory (sympathetic). Our findings are of clinical importance, since a better appreciation of the basic erectile mechanism is essential for successful management of erectile dysfunction.