On the autonomic innervation of the human vas deferens

Alpha1-adrenergic blockers selectively antagonize the contractions induced by 6-nitrodopamine in the human vas deferens

6-Nitrodopamine (6-ND) is released from human vas deferens and plays a modulatory role in the male ejaculation. Therapeutical use of α1-adrenoceptor antagonists is associated with ejaculatory abnormalities. To evaluate the effect of α1-adrenoceptor antagonists on the contractions induced by 6-ND, dopamine, noradrenaline, and adrenaline in the human epididymal vas deferens (HEVD). HEVD strips were suspended in glass chambers containing heated and oxygenated Krebs-Henseleit's solution. Cumulative concentration-response curves to catecholamines (10 nM-300 μM) were constructed in HEVD strips pre-incubated (30 min) with doxazosin (0.1-1 nM), tamsulosin (1-10 nM), prazosin (10-100 nM) and/or silodosin (0.1-10 nM). The effects of these α1-adrenoceptor antagonists were also evaluated in the electric-field stimulation (EFS, 2-32 Hz)-induced contractions. Doxazosin (0.1 nM) caused significant reductions in 6-ND-induced HEVD contractions without affecting the contractions induced by dopamine, noradrenaline, and adrenaline. Similar results were observed with tamsulosin (1 nM) and prazosin (10 nM). At these concentrations, these α1-adrenoceptor antagonists largely reduced the EFS-induced contractions. Silodosin (1 nM) caused concentration-dependent rightward shifts of the concentration-response curves to 6-ND but had no effect on the contractions induced by dopamine and adrenaline. Silodosin (0.1 nM) only inhibited the contractions induced by noradrenaline. Silodosin at 1 nM, but not at 0.1 nM, caused significant reductions in the EFS-induced contractions. The results reinforce the concept that 6-ND plays a major role in the human vas deferens contractility and indicate that the ejaculation disorders caused by doxazosin, tamsulosin, prazosin and silodosin cause in man, may be due to inhibition of the contractions induced by 6-ND rather than by the classical catecholamines dopamine, noradrenaline, and adrenaline.

Anatomy and physiology of genital organs - men

Male sexual functions involve a number of organs and structures in genitalia whose role is to produce fertilizing gametes and to allow female-partner insemination. The testes belong to the reproductive and endocrine systems as they synthesize spermatozoa and androgens, and are under finely regulated hormonal control by the hypothalamopituitary axis. Sexual responses are controlled by a complex and coordinated interplay of both the somatic and the autonomic nervous system in multiple components of the brain, spinal cord, and relevant peripheral organs. Erectile bodies are an essential element of the penis and engorgement of the penis with blood leads to penile tumescence. Blood engorgement is due to relaxation of smooth-muscle cells of erectile tissue and endothelium of the penile arteries. The penis gains additional rigidity when the ischiocavernosus muscles contract. Stimuli from peripheral and/or central origins activate particular spinal nuclei, causing penile erection. Ejaculation consists of two phases, emission and expulsion, which correspond, respectively, to secretion of the different components of the semen by sex glands and forceful expulsion of semen due to rhythmic contractions of the bulbospongiosus muscle. A spinal generator of ejaculation integrates genital stimuli and sexual cues and, when the excitatory threshold is reached, triggers ejaculation by orchestrating the activation of autonomic and somatic pathways commanding the peripheral events of ejaculation.

Merkel Cells in the Vellus Hair Follicles of Human Facial Skin: A Study Using Confocal Laser Microscopy

Many cases of Merkel cell carcinoma have recently been reported, and most of them have been localized on the facial skin. In this study, we investigated Merkel cells in the vellus hair follicles of facial region to characterize these cells in human subjects. Skin specimens doubly stained with cytokeratin (CK) 20 and either protein gene product (PGP) 9.5 or vasoreactive intestinal polypeptide (VIP) were examined by confocal laser microscopy. Many of the Merkel cells in the vellus hair follicles of the facial skin were localized in the bulge area. Some of these cells were attached to nerve terminals, although most of them were not associated with them. Our results suggest that there are two types of Merkel cells in the bulge area of the vellus hair follicles of facial skin: cells wholly unassociated with the nerve terminals and cells associated with thin nerve fibers. We postulate that the former cells may be undifferentiated (immature) and the latter differentiated (mature). If this is so, there is a chance that Merkel cell carcinoma originates from the undifferentiated Merkel cells in the bulge of the vellus hair with the formation of tumor masses in the dermis and no involvement of the epidermis. The Merkel cells connected with nerve fibers may secrete endocrine substances via a regulation of autonomic nerves.

Purinergic signalling in the reproductive system in health and disease

There are multiple roles for purinergic signalling in both male and female reproductive organs. ATP, released as a cotransmitter with noradrenaline from sympathetic nerves, contracts smooth muscle via P2X1 receptors in vas deferens, seminal vesicles, prostate and uterus, as well as in blood vessels. Male infertility occurs in P2X1 receptor knockout mice. Both short- and long-term trophic purinergic signalling occurs in reproductive organs. Purinergic signalling is involved in hormone secretion, penile erection, sperm motility and capacitation, and mucous production. Changes in purinoceptor expression occur in pathophysiological conditions, including pre-eclampsia, cancer and pain.

Ejaculatory dysfunction

Ejaculatory dysfunction may occur after many different disorders ranging from traumatic spinal cord injury to diabetes mellitus. With an understanding of the many facets and nuances of the ejaculatory apparatus, both anatomic and neurologic, the well-versed clinician can proceed along a safe, efficient, and appropriate treatment algorithm to help affected men and their partners achieve parenthood.

Physiological and pharmacological aspects of the vas deferens-an update

The vas deferens, a muscular conduit conveying spermatozoa from the epididymis to the urethra, has been used as a model tissue for smooth muscle pharmacological and physiological advancements. Many drugs, notably α-adrenergic antagonists, have effects on contractility and thus normal ejaculation, incurring significant side effects for patients that may interfere with compliance. A more thorough understanding of the innervation and neurotransmitter pharmacology of the vas has indicated that this is a highly complex structure and a model for co-transmission at the synapse. Recent models have shown clinical scenarios that alter the vas contraction. This review covers structure, receptors, neurotransmitters, smooth muscle physiology, and clinical implications of the vas deferens.

Perspective on the role of P2X-purinoceptor activation in human vas deferens contractility

The contractile actions of α,β-methylene ATP (α,β-meATP) and ATP and the effects of K(+) channel blockers in longitudinal and circular muscles of human vas deferens were investigated with a view to clarifying the functional importance of P2X(1)-purinoceptor activation and K(+) channels in modulating contractility of the tissues. The results provide an experiment-based perspective for resolving differing reports on purinergic activation of the tissues and uncertain roles of large-conductance Ca(2+)-activated K(+) (BK(Ca)) and voltage-gated delayed rectifier K(+) (K(V)) channels. α,β-Methylene ATP (3-100 μm) evoked suramin-sensitive contractions of longitudinal muscle but rarely of circular muscle. ATP (0.1-3 mm) less reliably activated only longitudinal muscle contractions. These were enhanced by ARL 67156 (100 μm), but a different ectonucleotidase inhibitor, POM 1, was ineffective. Both muscle types were unresponsive to ADP-βS (100 μm), a P2Y-purinoceptor agonist. Longitudinal muscle contractions in response to α,β-meATP were enhanced by FPL 64176 (1 μm), an L-type Ca(2+) agonist, TEA (1 mm), a non-specific K(+) channel blocker, 4-aminopyridine (0.3 mm), a selective blocker of K(V) channels, and iberiotoxin (0.1 μm), a selective blocker of BK(Ca) channels. Quiescent circular muscles responded to α,β-meATP reliably in the presence of FPL 64176 or iberiotoxin. Apamin (0.1 μm), a selective blocker of small conductance Ca(2+)-activated K(+) (SK(Ca)) channels had no effect in both muscle types. Y-27632 (1-10 μm) reduced longitudinal muscle contractions in response to α,β-meATP, suggesting involvement of Rho-kinase-dependent contractile mechanisms. The results indicate that P2X(1)-purinoceptor stimulation elicits excitatory effects that: (a) lead to longitudinal muscle contraction and secondary activation of 4-aminopyridine-sensitive (K(V)) and iberiotoxin-sensitive (BK(Ca)) K(+) channels; and (b) are subcontractile in circular muscle due to ancillary activation of BK(Ca) channels. The novel finding of differential action by P2X(1)-purinoceptor agonists in the muscle types has functional implication in terms of the purinergic contribution to overall contractile function of human vas deferens. The modulatory effects of K(V) and BK(Ca) channels following P2X(1)-purinoceptor activation may be pivotal in providing the crucial physiological mechanism that ensures temporal co-ordination of longitudinal and circular muscle contractility.

Human epididymal and prostatic tracts of vas deferens: Different contraction response to noradrenaline stimulation in isolated organ bath assay

In the present study epididymal and prostatic portions of human vas deferens were separately isolated and stimulated with exogenous noradrenaline to study their contractile properties. The results displayed that the epididymal tract produced a phasic-tonic response, while the prostatic strip produced only a phasic response suggesting a different functional role of each vas deferens segment. Moreover, it has been verified if alpha(1)-adrenoceptor antagonists doxazosin, alphuzosin and terazosin could differently block the noradrenaline response in each segment. Doxazosin, the most potent antagonist, displayed similar potency in epididymal and prostatic tract (pA(2)=8.51 and 8.42, respectively). Analogously, alphuzosin, although less potent than doxazosin, displayed in the same tracts a superimposed potency (pA(2)=7.25 and 7.30, respectively). In contrast with doxazosin and alphuzosin, terazosin displayed higher potency in blocking the contractile response in prostatic tract (pA(2)=7.67) than in epididymal segment (pA(2)=6.43). These results showed that alpha(1)-adrenoceptor antagonists doxazosin and alphuzosin, although with a different potency, did not discriminate between epididymal and prostatic segment while terazosin showed high potency in prostatic tract and only a moderate activity in epididymal section. Moreover, the biological model employed in our experiments could be a valid screening method to test the potential interferences of drugs indicated for bladder outlet obstruction with the peristaltic activity or the global tone of the human vas deferens.

On the intrinsic innervation of the epididymis of the camel (Camelus dromedarius)

The innervation of the camel epididymis was studied in 26 apparently healthy, sexually mature animals aged between 4 and 12 years. The material was collected during the different seasons of the year. Generally, five samples were taken from each epididymis. To demonstrate the general innervation pattern, immunohistochemical reactions to protein gene product-9.5, neurofilaments and neuron-specific enolase were used, in addition to acetylcholinesterase histochemistry. The nerve supply of the epididymis comes from two sources: (1) The majority of fibers come from the N. spermaticus inferior and accompany the deferent duct. (2) Another contribution stems from the N. spermaticus superior and enters the head region of the epididymis. From the exterior, the nerves penetrate the capsule of the organ to reach the interductular connective tissue. The terminal ramifications are observed directly within the wall of the duct and the wall of the epididymal arteries. The veins of the camel epididymis are not innervated. In the wall of the ductus epididymidis, the nerve fibers form plexuses at the subepithelial level and in the muscular coat. The amount of nerve fibers increases from the head to the tail, paralleling an increase in the intrinsic musculature. The intramural and interductular innervation of epididymal body and tail shows clear seasonal variations: More fibers and stronger reactions are observed during the winter season; the lowest density and the weakest reactions occur during the summer season. All epididymal nerves of the camel are unmyelinated. The majority of the intramural fibers and all in the arterial wall represent postjunctional sympathetic axons, but in the intramural plexuses of the duct a considerable number of cholinergic fibers are also present. Neuropeptide Y is the most frequent peptidergic transmitter and generally co-localized with dopamine-beta-hydroxylase in the sympathetic axons. Vasoactive intestinal polypeptide has a distribution similar to that of the cholinergic fibers. Calcitonin gene-related peptide-positive axons occur in moderate numbers, but never in the arterial innervation. Together with the relatively rare substance P-containing fibers, the calcitonin gene-related peptide-positive axons seem to represent the only sensory nerves in the camel epididymis.

The distribution of vesicular acetylcholine transporter in the human male genitourinary organs and its co-localization with neuropeptide Y and nitric oxide synthase

Because doubt still remains concerning the distribution of nerves that are unequivocally cholinergic in the human genitourinary organs, we have used a specific marker, namely, an antibody to vesicular acetylcholine transporter (VAChT), to immunolabel cholinergic axons and cell bodies in specimens of urinary bladder, seminal vesicle, vas deferens, and prostate gland obtained from neonates and children post mortem. In addition some sections were double-immunolabeled with VAChT and either neuropeptide Y (NPY) or nitric oxide synthase (NOS). The results demonstrated a rich cholinergic innervation to the muscle coat of the bladder body with a much less prominent, but nonetheless significant, cholinergic innervation to the smooth muscle components of the seminal vesicle, vas deferens, and prostate. Small ganglia were scattered throughout the detrusor muscle of the urinary bladder, approximately 75% of the intramural neurons being VAChT immunoreactive, whereas approximately 95% contained NPY and approximately 40% contained NOS. VAChT immunoreactivity was observed in 40% of neurons in ganglia scattered throughout the pelvic plexus. Almost all these cholinergic neurons contained NPY and approximately 65% contained NOS. Almost all the cholinergic nerve fibers throughout the genitourinary organs also contained NPY. Although NOS was sparse in the cholinergic nerves of the bladder body, it occurred in the majority of cholinergic nerves at the bladder neck and was also present in a proportion of the cholinergic nerves in the other organs examined. VAChT-immunoreactive nerves were also observed in a sub-epithelial location in all the organs examined, the majority containing NPY, whereas a small proportion contained NOS. Although doubt remains about the function of sub-epithelial cholinergic nerves in the urinary bladder, the majority of similar nerves in the seminal vesicle, vas deferens, and prostate gland are considered to be secretomotor. Collectively these findings demonstrate that the cholinergic innervation of the male genitourinary system is well established in the neonate and child. Neurourol. Urodynam. 19:185-194, 2000.

Colocalisation of neuropeptides, nitric oxide synthase and immunomarkers for catecholamines in nerve fibres of the adult human vas deferens

Single and double-label immunofluorescence methods were used to determine the distribution and patterns of colocalisation of various neuropeptides and nitric oxide synthase (NOS) with the catecholamine synthesising enzymes tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DbetaH) in nerve fibres within specimens of adult human vas deferens obtained at vasectomy (age range 28 to 83 y). Cholinergic nerve fibres were immunolabelled with an antiserum to vesicular acetylcholine transporter (VAChT). Using the general nerve marker protein gene product 9.5 (PGP) the density of intramural nerve fibres was found to be similar irrespective of age. Many of these axons, especially in the outer 2 muscle layers were TH and DbetaH-immunoreactive (IR) and were thus confirmed as noradrenergic. Fewer such axons were seen in the inner longitudinal muscle layer. All the noradrenergic nerve fibres also displayed NPY-immunoreactivity with minor populations containing galanin (GAL) or somatostatin (SOM). Nerve fibres lacking TH and DbetaH-IR were immunoreactive for VAChT and were sparsely distributed throughout the 2 outer muscle layers but more numerous in the inner muscle layer. Nerves lacking TH and DbetaH were immunoreactive for NPY and some also contained NOS, VIP or CGRP. These results have been compared with those obtained previously from specimens of human neonatal and infant vas deferens where, in contrast to the present results, NOS and VIP were shown to be colocalised with TH in many of the intramuscular nerve fibres. It thus appears that NOS and VIP cease their coexistence with TH in intramuscular nerve fibres of the human vas deferens between the pre- and postpubertal states. In addition to the intramuscular nerve fibres a VAChT-IR subepithelial nerve plexus occurs in the vas deferens and may control the secretory activity of the lining epithelium. Most of these subepithelial nerve fibres were immunoreactive for NPY and many also contained VIP while minor populations were immunoreactive for NOS, GAL, SOM or SP although fibres containing CGRP were not observed. The neuropeptide content of the subepithelial nerve plexus was similar to that observed in the infant, except for an increased density of VIP-IR nerves, which may reflect greater activity of the lining epithelial cells in the adult vas deferens.

Unusual autonomic ganglia: connections, chemistry, and plasticity of pelvic ganglia

The pelvic ganglia provide the majority of the autonomic nerve supply to reproductive organs, urinary bladder, and lower bowel. Of all autonomic ganglia, they are probably the least understood because in many species their anatomy is particularly complex. Furthermore, they are unusual autonomic ganglia in many ways, including their connections, structure, chemistry, and hormone sensitivity. This review will compare and contrast the normal structure and function of pelvic ganglia with other types of autonomic ganglia (sympathetic, parasympathetic, and enteric). Two aspects of plasticity in the pelvic pathways will also be discussed. First, the influence of gonadal steroids on the maturation and maintenance of pelvic reflex circuits will be considered. Second, the consequences of nerve injury will be discussed, particularly in the context of the pelvic ganglia receiving distributed spinal inputs. The review demonstrates that in many ways the pelvic ganglia differ substantially from other autonomic ganglia. Pelvic ganglia may also provide a useful system in which to study many fundamental neurobiological questions of broader relevance.

Sympathetic efferent pathways projecting to the vas deferens

The abdominal and pelvic sympathetic nervous system controlling the vas deferens has elaborate mechanisms to preserve its function against various injuries. The main sympathetic signals to the vas deferens proceed the common pathway in mammalians, which consists of the lumbar splanchnic nerve, caudal mesenteric plexus, hypogastric nerve, pelvic plexus and its branches. On the way of this common pathway, some signals cross to the other side of the body at the level of the caudal mesenteric plexus and/or the pelvic plexus. The preganglionic axons passing through the hypogastric nerve very likely provide a bilateral innervation to postganglionic neurons in the pelvic plexuses, which also exhibit crossing to the bilateral vasa deferentia. The sympathetic nerves originating from the thoracic spinal cord are of minor importance in contraction of the vas deferens but possibly influence it by the hormonal system consisting of the major splanchnic nerve and the adrenal medulla. When the common pathway is interrupted, various compensatory mechanisms are generated: enhancement of the remaining sympathetic pathways or reorganization of synaptic connection in the pelvic plexus. Surgical reconstruction of the transected hypogastric nerve is possible and cross-innervation mechanism via the hypogastric nerve can also be preserved. Elevation of intraluminal pressure at the cauda epididymis/proximal vas deferens induced by nerve impulse pushes the spermatozoa out to the ampulla and distention of the wall of the ampulla triggers its contraction to emit the content into the urethra. After seminal emission, a portion of the seminal fluid remaining in the vas deferens moves in a retrograde direction to the cauda epididymis for the next emission. It remains to be seen whether similar mechanisms in animals are at work in humans.

Structure and autonomic innervation of the human vas deferens: a review

The motor innervation of the smooth muscle coat of the human vas deferens is predominantly noradrenergic in type while a less dense and differently distributed presumptive cholinergic innervation is also in evidence, although the precise role of the latter is undetermined. Immunohistochemical studies have confirmed the presence of catecholamine-synthesizing enzymes tyrosine hydroxylase (TH) and dopamine beta hydroxylase (DbetaH) in the majority of fine, varicose intramuscular nerves, about two-thirds of which also contain neuropeptide Y (NPY). Minor populations of noradrenergic nerves contain enkephalin (ENK), galanin (GAL), somatostatin (SOM), or nitric oxide synthase (NOS). The presumptive cholinergic intramuscular nerves contain vasoactive intestinal polypeptide (VIP) and NPY. The subepithelial nerves of the vas deferens are assumed to have a secretomotor function and are rich in acetylcholinesterase and NPY, many also containing either VIP or NOS. The muscle coat of the human vas deferens is poorly differentiated until after birth, the intramuscular nerves in the fetus being relatively thick and non-varicose. Development of a subepithelial nerve plexus lags behind that in the muscle coat but its density in the neonatal vas deferens resembles that seen in the adult. Observations on specimens of human vas deferens obtained at vasovasostomy carried out 1 to 15 years after vasectomy have shown a marked reduction in the density of noradrenergic nerves in the muscle coat of the testicular portion while that in the urethral portion remains unaltered. Furthermore, the subepithelial secretomotor nerves degenerate in the testicular portion. These long-term changes 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.

Origin and neurochemical characteristics of nerve fibres supplying the mammalian vas deferens

The present paper deals with the origin and neurochemical characteristics of autonomic postganglionic and sensory nerve fibres supplying the mammalian vas deferens. The vas deferens is innervated by postganglionic nerve fibres originating primarily from neurons in pelvic ganglia and, to a lesser extent, from neurons in the inferior mesenteric ganglion and sympathetic chain ganglia as well as by sensory nerve fibres arising from dorsal root ganglia. Three major populations of nerve terminals innervating the organ can be distinguished: (1) noradrenergic fibres; (2) cholinergic fibres containing vasoactive intestinal polypeptide, neuropeptide Y, nitric oxide synthase, and (in the pig) somatostatin, supplying particularly the lamina propria; and (3) non-noradrenergic, presumably sensory fibres, containing calcitonin gene-related peptide and/or substance P. The population of noradrenergic nerves is the most common. In the pig, it can be divided into three subpopulations: a somatostatin-containing, a Leu-enkephalin-containing and a subpopulation immunonegative to these peptides, in descending order of magnitude. In the rat, guinea-pig, and man, NPY seems to be the most common peptide occurring in the noradrenergic axons. In the pig, coexistence patterns of the substances existing within nerve fibres supplying the vas deferens blood vessels are clearly different from those found in nerve fibres innervating the organ wall. The majority of the noradrenergic fibres associated with blood vessels contain neuropeptide Y only, while non-noradrenergic perivascular nerves contain predominantly vasoactive intestinal polypeptide. The possibility of different sources of origin of the particular nerve fibre subpopulations supplying the mammalian vas deferens and its blood vessels is discussed.

The vesico-ureteric junction in three cases of primary obstructive megaureter associated with ectopic ureteric insertion

OBJECTIVE

To examine the histological structure and autonomic innervation of the vesico-ureteric junction (VUJ) in three cases of primary obstructive megaureter occurring in association with ectopic ureteric insertion.

PATIENTS AND METHODS

Specimens of VUJ were obtained from one male and two females with primary obstructive megaureter and ectopic ureteric insertions. Serial frozen sections were cut and stained with either Masson's trichrome or immunostained for protein gene product (PGP 9.5; a general nerve marker) or dopamine beta-hydroxylase (DbetaH), a marker for noradrenergic nerves.

RESULTS

In each case examined the terminal ureter was encircled by a thick collar of smooth muscle on the inside of which lay normal narrow-diameter longitudinally orientated ureteric muscle bundles. Loose connective tissue separated the surrounding detrusor muscle from this abnormal muscle collar, which was formed of distinctive smooth muscle cells arranged in a meshwork. The autonomic innervation of the ureteric and detrusor muscle bundles was similar to that previously reported for the normal VUJ while the thick muscle collar was richly innervated by DbetaH-immunoreactive noradrenergic nerves.

CONCLUSION

The presence of an additional smooth muscle collar surrounding the terminal ureter may impede the normal flow of urine from ureter to bladder and be the cause of megaureter in these patients. We propose that the presence of this muscular collar arises from the developmental anomaly and suggest that these cases represent a subgroup that requires early surgical treatment.

Development of peptide-containing nerves in the human fetal vas deferens and seminal vesicle

OBJECTIVE

To use immunohistochemical methods to study the developing autonomic innervation of the human fetal vas deferens and seminal vesicle.

MATERIAL AND METHODS

Thirteen pre-natal specimens ranging in gestational age from 13 to 30 weeks were acquired following abortion or miscarriage. The overall innervation of each specimen was visualized using protein gene product 9.5 (PGP), a general nerve marker, while the onset and development of specific neuropeptide-containing sub-populations were investigated using antisera to neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), substance P (SP), calcitonin gene related peptide (CGRP), bombesin (BOM), somatostatin (SOM), and met-enkephalin (ENK). In addition the occurrence and distribution of presumptive noradrenergic nerves was studied using antisera to dopamine-beta-hydroxylase (D beta H) and tyrosine hydroxylase (TH).

RESULTS

At 13 weeks numerous PGP, D beta H, TH, NPY and ENK immunoreactive (-IR) nerve trunks were present in the adventitia of the vas deferens and seminal vesicle but at this stage nerve fibres were not present in the smooth muscle coat of either organ. By 17 weeks, fine PGP-, D beta H, and TH-IR nerve fibres had penetrated the outer aspect of the muscle coat of the seminal vesicle but not the vas deferens. At 20 weeks a branching network of PGP-, D beta H- and TH-IR nerve fibres occurred throughout the full thickness of the muscle coat of the seminal vesicle while similar nerves were present only in the outer half of the muscle coat of the vas deferens. At 23 weeks the full thickness of the muscle coat of the vas deferens was richly innervated by a branching plexus of PGP-IR nerves. Many of these adventitial and intramuscular nerves were immunoreactive for D beta H or TH while some were immunoreactive for either NPY or ENK. Occasional adventitial nerves were immunoreactive for SP or CGRP, these being first observed at 20 weeks. VIP-IR nerves were extremely rare in the muscle coat of either organ, being first observed at 17 weeks in the seminal vesicle and at 20 weeks in the vas deferens where they mainly formed perivascular plexuses. PGP-IR nerves were first observed in the submucosa of the seminal vesicle at 20 weeks and in the vas deferens at 21 weeks. Some of these nerves were perivascular in location while other formed a subepithelial plexus which increased in density with increasing gestational age. At 22 weeks of gestation some of the submucosal nerves were immunoreactive for SP or NPY, while at 30 weeks NPY-IR nerves formed the majority of subepithelial nerves. Occasional VIP-IR subepithelial nerves were first observed at 26 weeks but were extremely rare even at 30 weeks. Submucosal nerves immunoreactive for CGRP, D beta H, TH or ENK did not occur in any of the specimens examined.

CONCLUSION

(i) From 13 weeks gestation autonomic nerves develop in the muscle coat of the fetal seminal vesicle and vas deferens, being denser in the seminal vesicle than the vas deferens up to 23 weeks gestation. (ii) The majority of the intramuscular nerves in either organ contain D beta H, TH, NPY and ENK and are presumably noradrenergic in type. (iii) A subepithelial nerve plexus develops around 20 weeks gestation and contains NPY but not VIP, unlike the adult organs. (iv) Scattered neuroendocrine cells immunoreactive for SOM are present in the mucosa of the seminal vesicle from 23 weeks of gestation.

Origin of neurons supplying the vas deferens of the rat

Retrograde axonal tracing methods using Fluoro-Gold were used to examine the neuronal input to the vas deferens in the adult Wistar rat. The greatest number of labelled efferent neurons were found in the ipsilateral pelvic accessory ganglion (PAG) (68%) and the major pelvic ganglion (MPG) (15%). Fewer than 3% of labelled neurons were localized to the inferior mesenteric and sympathetic chain ganglia. Labelled neurons were also located in the ipsilateral L1, L2, and L6, S1 dorsal root ganglia (DRG), corresponding to afferents that travel in the hypogastric and pelvic nerves, respectively. Contributions from contralateral neurons in the PAG, MPG and L1 DRG were also documented. The role of afferents supplying the vas deferens is not known but they may relay nociceptive or mechanoreceptive input. Efferent input from peripheral ganglia probably contributes to contractility of the vas deferens based on previous investigations.

Cholinergic receptors in the human vas deferens

This study represents the first investigation demonstrating the contractile response to exogenous acetylcholine (ACh) in the isolated human vas deferens. Pharmacological characterization of cholinergic receptors was achieved using selective antagonists to define receptor subtypes. In the HVD the effect of exogenous ACh is revealed as a dose-dependent sudden increase in the basal tension of the vasa. The ACh receptors of the HVD were competitively antagonized by atropine (ATR) with a high pA2 value (8.78). The main finding of this study is the presence of cholinergic receptors of the pharmacologically defined M1-ACh subtype in the isolated HVD, according to the pA2 values obtained with pirenzepine (PRZ) 7.39, AF-DX 116 (AF) 5.92 and 4-DAMP 5.65, M1-ACh, M2-ACh and M3-ACh selective antagonists, respectively. Prazosin (PZ), a selective alpha 1-adrenergic antagonist, displayed a similar competitive antagonism for the contractile response evoked both by ACh (pA2 = 8.69) and NE (pA2 = 8.58) in the HVD. The antagonism exerted by PZ on the ACh-induced contractile response of the HVD, suggests that ACh probably acts at a presynaptic level stimulating the release of NE from an adrenergic neuron. According to these findings, the receptor involved in this action, located in the proximity of the nerve terminals, seems to be of the M1-ACh subtype.

Immunoreactive arginine vasopressin (AVP) and effects of AVP in the human vas deferens

Immunoreactive (IR) arginine vasopressin (AVP) was found to occur in the epididymal part of the human vas deferens. Segments from nine different subjects all contained IR-AVP in concentrations ranging from 37 to 717 fmol/gm. wet weight, concentrations severalfold higher than those normally found in the circulation. IR-AVP was shown by high performance liquid chromatography to elute in the same position as synthetic AVP. AVP added to isolated preparations of the human vas deferens induced concentration-related repetitive phasic contractions without significant changes of baseline tension. These contractions seemed to be mediated via stimulation of vasopressin V1-receptors and were abolished in the presence of vasopressin antagonists. Contractions induced by electrical field stimulation were frequency-dependent and sensitive to tetrodotoxin and prazosin. They were not affected by the vasopressin antagonists used. AVP increased the response to electrical field stimulation and this effect was inhibited by vasopressin antagonists. The results suggest either that circulating AVP is taken up and accumulated by the human vas deferens, and/or that AVP is synthesized locally. They do not suggest co-release of AVP and noradrenaline from nerve endings. The physiological role of the AVP occurring in the human vas deferens remains to be established.

The effects of vasectomy on the autonomic innervation of the human vas deferens

Neurohistochemical and fine structural techniques have been employed to examine the intramural autonomic innervation of the human vas deferens following surgical division of the duct one to 15 years previously. Samples from sites on the distal (testicular) and proximal (urethral) aspects of the original vasectomy have been compared with control specimens obtained at vasectomy as to the arrangement and distribution of autonomic nerves. In contrast with tissue from the proximal part and from controls, the distal samples revealed a marked reduction in the noradrenergic innervation of the muscle coat. In addition acetylcholinesterase-containing nerves associated with the basal aspect of the epithelium were usually absent from the distal portion of the vas deferens. These findings have been considered in relation to the contractile and secretory activities of the organ following vasovasostomy and may be of importance to the maturation and fertility of spermatozoa.

Effect of drugs interacting with adrenoreceptors and muscarinic receptors in the epididymal and prostatic parts of the human isolated vas deferens

Electrical field stimulation of ring preparations of the epididymal (Ve) and prostatic (Vp) parts of the human isolated vas deferens produced contractions with similar frequency-dependence and appearance. The contractions of Ve, but not of Vp preparations were abolished by tetrodotoxin (10(-6)M). Noradrenaline (NA), phenylephrine, and methoxamine, but not clonidine induced repetitive, phasic contractions in both Ve and Vp preparations, and increased the amplitude of electrically induced responses. Clonidine concentration-dependently decreased electrically induced contractions in Ve preparations, but had no significant effects in Vp preparations. Phentolamine and prazosin abolished electrically induced contractions in Ve but not in Vp preparations. In Ve rings the contractions were increased by rauwolscine; no such effect was observed in Vp preparations. Isoprenaline, propranolol, acetylcholine and carbachol had no effects in the Ve or Vp preparations. Scopolamine and atropine reduced electrically induced responses. Clonidine decreased and rauwolscine increased the electrically induced release of 3H in both Ve and Vp preparations pre-loaded with 3H-NA. Phenylephrine, prazosin, isoprenaline, propranolol, carbachol and scopolamine had minor or no effects on the 3H release. Radioligand receptor binding experiments using 3H-prazosin and 3H-rauwolscine as ligands revealed similar densities of alpha 1- and alpha 2-adrenoreceptors in the human vas deferens. There seemed to be no differences in their distribution between the epididymal, middle and prostatic part of the organ. It is concluded that the neurotransmission in the human vas deferens is noradrenergic and mediated via alpha 1-adrenoreceptors. The prazosin and tetrodotoxin resistant part of the electrically induced contraction in Vp preparations may be caused by direct smooth muscle stimulation.

Aperistalsis of the vas deferens corrected with administration of ephedrine

An infertile patient with azoospermia, normal spermatogenesis on a testis biopsy and no sperm seen on a post-ejaculate urinalysis underwent bilateral scrotal exploration. Normal anatomy was found at exploration and bilateral vasograms demonstrated the absence of obstruction. After subsequent therapy with ephedrine semen analysis showed a total sperm count of 72 million.