Studies on intracavernosal VIP levels during pharmacologically induced penile erections.

Intracavernosal and peripheral venous vasoactive intestinal polypeptide (VIP) levels were measured in men with predominantly organic or predominantly psychogenic impotence. The measurements were taken at intervals up to 30 min following intracavernosal injections of saline, papaverine hydrochloride and papaverine hydrochloride and phentolamine. Levels were also measured after tactile and visual sexual stimulation and following an intravenous injection of papaverine and phentolamine. A penile erection occurred in all men receiving intracavernosal vasoactive compounds. The mean VIP concentration did not alter significantly in either cavernosal or peripheral venous blood during the erection. Mean VIP concentrations were significantly greater in the neurogenic (all diabetic) group than in the other groups studied. Mean cavernosal and peripheral VIP concentrations did not alter following tactile or visual sexual stimulation and no significant alteration in mean peripheral venous VIP concentration occurred following injection of papaverine and phentolamine. The putative role of VIP in the induction of penile erection has not been elucidated in these studies.