Js. Dixon et al., STRUCTURE AND AUTONOMIC INNERVATION OF THE HUMAN VAS-DEFERENS - A REVIEW, Microscopy research and technique, 42(6), 1998, pp. 423-432
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.