Somatic innervation contributes to the release of bulbourethral gland secretion in male rats.

BACKGROUND: In male rats, the bulbourethral glands (Bu-Gs) are the unique accessory sexual glands surrounded by striated musculature. However, until now the role of this musculature was unknown. OBJECTIVES: (i) To characterize the Bu-Gs striated muscular layer in male rats and determine its innervation and response to genital stimulation. (ii) To reveal the role of the Bu-Gs striated musculature in the release of glandular secretion. (iii) To elucidate the effect of bilateral ablation of the Bu-Gs on copulatory behavior and seminal fluid characteristics. MATERIALS AND METHODS: Adult Wistar male rats were allocated in three experiments: in Experiment 1, the Bu-Gs striated musculature, innervation and reflex activity were determined by gross anatomy and histological and electrophysiological techniques; electromyographic activity of the Bu-Gs striated musculature was evoked with genital stimulation. In Experiment 2, Bu-Gs were analyzed after copulatory behavior of intact or animals with unilateral transected motor branch of the sacral plexus (MBSP). In Experiment 3, copulatory behavior and spermatobioscopy of males with bilateral ablation of the Bu-Gs or sham surgery were analyzed. RESULTS: The Bu-Gs striated fibers discharged in response to mechanostimulation of the prepuce, glans, and penile-urethra. Innervation of the Bu-Gs striated musculature originated from the MBSP; this nerve also innervates striated penile muscles. Unilateral transection of the MBSP significantly decreased the secretion from the ipsilateral Bu-G to the nerve transection. Bilateral ablation of Bu-Gs did not affect seminal plug formation but decreased semen viscosity. DISCUSSION AND CONCLUSION: The Bu-Gs striated musculature contributes to expel glandular secretion during sexual intercourse. The somatic control of Bu-Gs secretion is additional to the reported autonomic innervation supplied by the cavernosus nerve, which may underlie the synthesis of secretion as well as contraction of Bu-Gs smooth muscle.

Distribution and nerve pathways of neurons supplying the bulbourethral gland in the pig.

The present study has disclosed for the first time the distribution and peripheral nerve pathways of autonomic and primary afferent neurons projecting to the bulbourethral gland (BG) in a mammalian species, the pig (n = 5), using combined retrograde tracing and cutting the hypogastric (n = 3) or pelvic (n = 3) nerve. Neurons projecting to the right BG were found in pelvic ganglia (PG), sympathetic chain ganglia (SChG; L2-S3), the caudal mesenteric ganglion (CaMG) and dorsal root ganglia (DRG; L1-L3, S1-S3). In general, the majority (about 75%) of them were located in the ipsilateral ganglia. Results of denervation experiments suggest that the neurons located in CaMG, and lumbar SChG and DRG project through the hypogastric nerve while processes of those found in the sacral SChG and DRG travel through the pelvic nerve or pelvic branch of the pudendal nerve. Moreover, the results obtained also suggest that the 'crossing points' (i.e. the areas where nerve fibres reach the opposite side) for the neurons found in the contralateral CaMG are located partly at the level of this ganglion and, for a smaller number of the nerve cells, at the level of the pelvic plexus. The crossing points for the SChG and DRG neurons are probably situated at the level of sympathetic chains and, for sacral SChG neurons, at the level of the pelvic plexus. The diversity of sources of the nerve supply to the porcine BG corresponds well with the variety (as previously distinguished with immunohistochemistry) of its intrinsic nerve fibre populations.

Noradrenergic and cholinergic innervation of the accessory sexual glands in male sheep.

Immunohistochemistry was applied to determine the distribution patterns of nerve fibres containing tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DbetaH), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP) and vesicular acetylcholine transporter (VAChT) in the prostate, seminal vesicle (SV) and bulbourethral glands (BU) of male sheep. In all organs studied, cholinergic innervation was more developed than noradrenergic innervation. Numerous VAChT-immunoreactive (IR) nerve fibres were found in the muscular layer and mucosa of the SV and BU as well as in the prostate. A similar abundance of noradrenergic nerve fibres (showing immunoreactivity both to TH and DbetaH) was also found in both layers of the SV and BU (but not in the prostate). In the prostate a moderate density of VIP-IR nerve fibres was present but only very scarce NPY-IR nerve fibres were shown. All the studied accessory sexual glands (ASG) of male sheep contained VIP-IR nerve fibres in a similar frequency. Double immunohistochemistry revealed that the vast majority of noradrenergic nerve fibres also contained NPY. None of the noradrenergic nerve fibres showed the presence of VAChT or VIP. The possible functional significance of these findings is discussed.

Immunohistochemical characteristics of neurons supplying the porcine bulbourethral gland.

In the male pig, the bulbourethral gland (BG) is a particulary well developed accessory genital gland (AGG) which produces complex secretion contributing to the fluid component of semen. The secretory and motor function of AGGs is thought to be under the autonomic nervous system control. Although relatively much is known about the innervation of the prostate gland and, to a lesser degree, of the seminal vesicle, the paucity of data dealing with the innervation of BG is striking. Therefore, combined retrograde tracing and double-labelling immunofluorescence have been used to investigate the distribution and immunohistochemical properties of autonomic and primary afferent neurons projecting to this gland in the pig. BG-projecting neurons were found in some ipsilateral (I) and contralateral (C) sympathetic chain ganglia (SChG), the caudal mesenteric ganglion (CaMG), pelvic ganglia (PG) and some dorsal root ganglia (DRG). Immunohistochemistry revealed that the vast majority of CaMG and SChG BG-projecting neurons contained tyrosine hydroxylase (TH) and dopaminebeta-hydroxylase (DbetaH), and some neuropeptides including neuropeptide Y (NPY), somatostatin (SOM) and galanin (GAL). Three subpopulations of PG neurons supplying BG could be distinguished: 1) cholinergic neurons [vesicular acetylcholine transporter (VAChT)-positive] which also contained vasoactive intestinal polypeptide (VIP), nitric oxide synthase (NOS), SOM and NPY, 2) adrenergic neurons (TH-positive) which also stained for NPY, GAL or leu5-enkephalin (LEU), and 3) non-adrenergic, non-cholinergic neurons (NANC). DRG BG-projecting neurons contained mostly substance P (SP) and/or calcitonin gene-related peptide (CGRP) which sometimes colocalized with GAL. The possible functional significance of the substances found within the neurons is discussed.

Adrenergic innervation of the epididymis, vas deferens, accessory genital glands and urethra in the boar.

The distribution of adrenergic nerve fibres in the urethra and some organs of the male reproductive system of juvenile boars was studied by applying the glioxylic acid-induced fluorescence method. Adrenergic nerve fibres were found in all structures examined, with particular relation to their muscular coats and arterial blood vessels. Ductuli efferentes and ductus epididymidis from the caput region were weakly innervated. The number of adrenergic nerve fibres innervating the ductus epididymidis gradually increased towards the cauda epididymidis, being greatest in this region. The vas deferens was very well supplied with these nerves. The seminal vesicle was found to be the richest innervated organ in comparison with other accessory genital glands. The body of the prostate was slightly weaker innervated, while the disseminated part of the prostate as well as the bulbourethral gland comprised the smallest number of adrenergic nerve fibres. The urethra received a very dense adrenergic nerve supply. The pelvic part of the urogenital duct possessed a moderate number of adrenergic nerves, which supplied not only the muscular membrane but also venous sinuses of the mucosa. In a close vicinity to the internal genital organs numerous ganglia containing both adrenergic and non-adrenergic nerve cell bodies were observed. The presented data suggest that adrenergic innervation may be deeply involved in the control of blood flow and motor function of the organs studied, and that a part of adrenergic nerve fibers innervating these structures may originate from pelvic ganglia.