Colocalization of vasoactive intestinal polypeptide and nitric oxide in penis-innervating neurons in the major pelvic ganglion of the rat.

By using a combination of fluorescent retrograde labeling and double immunofluorescence histochemistry, the present study revealed in the rat that the vast majority of major pelvic ganglion neurons innervating penile erectile tissue contained both vasoactive intestinal polypeptide (VIP) and nitric oxide synthase. The result suggests that VIP and nitric oxide may exert a cooperative action in penile erection.