STRUCTURE AND AUTONOMIC INNERVATION OF THE HUMAN VAS-DEFERENS - A REVIEW

The motor innervation of the smooth muscle coat of the human vas defer ens is predominantly noradrenergic in type while a less dense and diff erently distributed presumptive cholinergic innervation is also in evi dence, although the precise role of the latter is undetermined. Immuno histochemical studies have confirmed the presence of catecholamine-syn thesizing enzymes tyrosine hydroxylase (TH) and dopamine beta hydroxyl ase (DPH) in the majority of fine, varicose intramuscular nerves, abou t two-thirds of which also contain neuropeptide Y (NPY). Minor populat ions of noradrenergic nerves contain enkephalin (ENK), galanin (GAL), somatostatin (SOM), or nitric oxide synthase (NOS). The presumptive ch olinergic intramuscular nerves contain vasoactive intestinal polypepti de (VIP) and NPY. The subepithelial nerves of the vas deferens are ass umed to have a secretomotor function and are rich in acetylcholinester ase and NPY, many also containing either VIP or NOS. The muscle coat o f the human vas deferens is poorly differentiated until after birth, t he intramuscular nerves in the fetus being relatively thick and non-va ricose. Development of a subepithelial nerve plexus lags behind that i n the muscle coat but its density in the neonatal vas deferens resembl es that seen in the adult. Observations on specimens of human vas defe rens obtained at vasovasostomy carried out 1 to 15 years after vasecto my have shown a marked reduction in the density of noradrenergic nerve s in the muscle coat of the testicular portion while that in the ureth ral portion remains unaltered. Furthermore, the subepithelial secretom otor nerves degenerate in the testicular portion. These long-term chan ges in the pattern of innervation of the vas deferens consequent upon vasectomy may have profound effects upon the outcome of vasovasostomy with respect to subsequent sperm maturation, transport., and viability . (C) 1998 Wiley-Liss, Inc.