We recently reported the results of applying immunohistochemical methods to examine the distribution of neuropeptides and neurotransmitter synthesising enzymes in the autonomic nerve fibres of specimens of human vas deferens obtained at vasectomy (Jen et al. 1999). As anticipated from previous neurohistochemical and electron microscopic studies (Baumgarten et al. 1971), the majority of nerves supplying the muscle coat are noradrenergic in type as demonstrated by the presence of tyrosine hydroxylase (TH) and dopamine beta hydroxylase (DbH) (Dixon et al. 1998), both of which are enzymes involved in the synthesis of noradrenaline.

In addition to the profuse intramuscular plexus of nerves, a second nerve plexus occurs at the base of the epithelium lining the vas deferens. These subepithelial nerves are immunopositive for vesicular acetylcholine transporter (VAChT) and therefore cholinergic in type, presumably serving a secretomotor function (Jen et al. 1999). Our immunohistochemical studies have also shown the presence of neuropeptide Y (NPY) in most of these subepithelial nerves in the human vas deferens with minor populations containing vasoactive intestinal peptide (VIP) and nitric oxide synthase (NOS), an enzyme involved in the formation of nitric oxide.