Hemodynamic study of penile erection in dogs.

Full erection by the optimal electrical stimulation of the cavernous nerves was induced in dogs anesthetized with pentobarbital and the hemodynamics of the corpus cavernosum investigated. In 7 dogs, the divided internal pudendal arteries were cannulated and perfused with constant and adjustable arterial inflow. Before nerve stimulation, this increase in flow raised the intracorporeal pressure (ICP). The same change in flow during nerve stimulation resulted in an elevation of ICP. Furthermore, nerve stimulation at zero flow condition elicited a significant increase in ICP. The results suggest that full penile erection requires nerve stimulation during high flow state (constant flow above 25 ml/min). The ICP cannot reach a maximum by passive increase in flow alone. The increase in ICP by nerve stimulation at zero flow condition indicates the existence of a contractile element around the corpus cavernosum or the venous compartment. This mechanism may not be essential for penile erection, but it may serve to change the flow-pressure relationship in the corpus cavernosum.