Light and electron microscope demonstration of VIP- and enkephalin-immunoreactive nerves in the human male genitourinary tract.

Vasoactive intestinal polypeptide (VIP) and enkephalins were demonstrated in the nerves of the human male urogenital tract by light and electron microscope immunohistochemical techniques. Nerves containing immunoreactivity to VIP were more numerous than enkephalin-immunoreactive nerves. Both VIP- and enkephalin-immunoreactive nerves were detected in the vas deferens, prostate, seminal vesicles, and urinary bladder. In the kidney, testis, and epididymis no immunoreactive nerves could be demonstrated. By electron microscope both types of immunoreactivities were localized to the large granular vesicles of nerve terminals. VIP-immunoreactive nerves were mostly found subepithelially, whereas enkephalin-immunoreactive nerves were mainly related to smooth muscle cells. The possible functions of these peptide-containing nerves are discussed.