Lumbosacral sympathetic trunk as a compensatory pathway for seminal emission after bilateral hypogastric nerve transections in the dog

The Anatomy, Histology, and Function of the Major Pelvic Ganglion

This review provides a comprehensive analysis of the pelvic plexus and its regulation across various mammalian species, including rats, cats, dogs, and pigs. The pelvic and hypogastric nerves play crucial roles in regulating pelvic functions such as micturition, defecation, and erection. The anatomical organization of these nerves varies, forming either well-defined ganglia or complex plexuses. Despite these variations, the neurons within these structures are consistently regulated by key neurotransmitters, norepinephrine and acetylcholine. These neurons also possess receptors for testosterone and prolactin, particularly in rats, indicating the significant role of these hormones in neuronal function and development. Moreover, neuropeptides such as vasoactive intestinal peptide (VIP), substance P, neuropeptide Y (NPY), somatostatin (SOM), galanin (GAL), and calcitonin gene-related peptide (CGRP) are co-released with neurotransmitters to modulate pelvic functions. This review highlights the complex interplay between neurotransmitters, neuropeptides, and hormones in regulating pelvic physiology and emphasizes the importance of hormonal regulation in maintaining the functionality and health of the pelvic plexus across different species.

Origin of the primary efferent neurons projecting to the prostate of the dog

The retrograde tracing technique of neuronal tracer Fast Blue was used to determine sources of origin of efferent nerve fibers supplying the prostate of the dog. After injection of Fast Blue into the canine prostate retrogradely labelled neurons were found in bilateral L3-S3 sympathetic chain ganglia, bilateral caudal mesenteric ganglion and in bilateral pelvic plexus ganglia. No Fast Blue-positive neurons were present in bilateral L1-L2 sympathetic chain ganglia and in coeliac-mesenteric ganglion complex. The vast majority of Fast Blue-positive efferent prostate-projecting neurons (56.2% +/- 1.7) were located in bilateral caudal mesenteric ganglion, whereas 28.7% +/- 1.5 of them were located in bilateral pelvic plexus ganglia and 14.9% +/- 0.5 in bilateral L3-S3 sympathetic chain ganglia. Immunohistochemical staining for tyrosine hydroxylase and dopamine beta-hydroxylase was applied to determine the neurochemical character of Fast Blue-positive efferent neurons. Immunohistochemistry revealed that in all tyrosine hydroxylase immunoreactive Fast Blue-positive neurons immunoreactivity for dopamine beta-hydroxylase was also found (noradrenergic neurons) while all tyrosine hydroxylase-negative Fast Blue-positive neurons did not express dopamine beta-hydroxylase (non-noradrenergic neurons). In bilateral sympathetic chain ganglia, 96.4% +/- 2.1 of the prostate-projecting neurons were adrenergic and in bilateral caudal mesenteric ganglion this frequency amounted to 95.6% +/- 1.6. In bilateral pelvic plexus ganglia, 26.7% +/- 1.5 of the prostate-supplying efferent neurons did not express either tyrosine hydroxylase or dopamine beta-hydroxylase immunoreactivity which makes discussion of their cholinergic character possible.

Control of canine membranous urethra, bulbocavernosus and ischiocavernosus muscles by lumbosacral sympathetic pathways

The membranous urethral muscles, bulbocavernosus muscle (BCM) and ischiocavernosus muscle (ICM) play a significant role on expulsion at ejaculation. Projection of the sympathetic pathways in the retroperitoneum to these muscles was investigated in the dog. Intraluminar pressure of the membranous urethra and contractions of the BCM and ICM to electrical stimulation of the lumbar splanchnic nerve (LSN) or the lumbosacral sympathetic chain (LSC) were examined. Stimulation of the LSN was performed after transection of the unilateral hypogastric nerve (HGN) to clarify its cross-innervation. Stimulation of each of the 2nd to 4th LSNs elicited elevation of the intraluminal pressure of the membranous urethra. In eight dogs whose right HGNs were transected, 15 of the 19 right LSNs, and 12 of the 16 left LSNs examined elicited elevation of the membranous urethral pressure, respectively. In five dogs whose left HGNs were transected, 6 of the 9 right LSNs and 10 of the 12 left LSNs stimulated elicited elevation of the pressure. Stimulation of the HGN caused no detectable contractions of the BCM and ICM in all six dogs examined. Stimulation of the LSC elicited responses of the BCM and ICM in all six dogs examined and the membranous urethra in three of six dogs. The maximum value of the response of the BCM was greater than that of the ICM. After consecutive transection of the ipsilateral pelvic nerve, stimulation of the LSC showed no significant changes in the responses of the BCM and ICM. The above results indicate the following: (1). each of the L2-L4 LSNs sends signals to the membranous urethra via two routes, passing through the ipsilateral or contralateral HGN; (2). the above nerve does not send effective signals to the BCM and ICM; (3). the LSC sends signals to the membranous urethra, BCM and ICM; (4). the signals from the LSC mainly pass through the pudendal nerve to the BCM and ICM; and (5). the signals were dominant to the BCM compared with the ICM.

Spinal cord segments controlling the canine vas deferens and differentiation of the primate sympathetic pathways to the vas deferens

This study was undertaken to explore the spinal cord segments controlling the canine and human vas deferens and differentiation of the mammalian sympathetic pathways to the vas deferens. Thoracolumbar white communicating rami (WCR) were electrically stimulated in the dogs. Stimulation of the 1st, 2nd, 3rd, and 4th lumbar WCR elicited an elevation of intraluminal pressure of the vas deferens in 2, 10, 16, and 14 of 20 dogs examined, respectively, whereas stimulation of sympathetic chain (between the 13th thoracic and 1st lumbar ganglia), 13th thoracic WCR, intermesenteric plexus, and 5th lumbar WCR showed no response in any of the 10, 2, 12, and 5 dogs examined, respectively. Anatomical study of the 118 human lumbar splanchnic nerves of 55 cadavers showed that almost all lumbar splanchnic nerves (96%) originated from L2 and/or L3 sympathetic chain ganglia (L1-2 spinal cord levels). Comparative anatomical study of the mammalian sympathetic pathways to the vas deferens showed that the caudal mesenteric plexus is not divided in rats, rabbits, cats, and dogs and is partially divided into two plexuses in monkeys and completely in humans and that separation of the sympathetic component in the pelvic nerve (isolation of the sacral splanchnic nerve) is in progress in the primate. These results indicate that spinal cord segments controlling the vas deferens are L1-4 in the dog and probably L1-2 in humans and that differentiation of the sympathetic nerve pathways is proceeding at both main and compensatory pathways to the vas deferens in the primate.

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.

Preservation of ejaculatory function by reconstruction of the canine hypogastric nerve

OBJECT

The hypogastric nerve (HGN) plays a crucial role in the primary functions of ejaculation: sperm transport through the vas deferens, secretion of prostatic fluid, and bladder neck closure. This study was undertaken to explore the possibility of restoring HGN function to the seminal tract and preserving its cross-innervation mechanism to the seminal tract after HGN-HGN reattachment.

METHODS

Responses of the vas deferens/epididymis, prostate, and bladder neck to electrical stimulation of the lumbar splanchnic nerve (LSN) or the HGN and occurrence of antegrade ejaculation as a result of manual penile stimulation were examined in dogs that had undergone HGN-HGN reattachment. Eighteen months after the procedure had been performed bilaterally, 23 LSNs were electrically stimulated. In 17 LSNs this stimulation elicited elevation of vasal pressure (12 nerves bilaterally); in 18 LNs, bladder neck pressure; and in 15 LSNs, prostate contraction. After retransection of the right HGN in the dogs that had undergone HGN-HGN reattachment, 11 right-sided LSNs were stimulated; in seven LSNs, the stimulation elicited elevation of vasal pressure (five bilaterally), in seven bladder neck pressure, and in six prostate contraction. Twelve left-sided LSNs were stimulated; in seven LSNs, the stimulation elicited elevation of vasal pressure (four bilaterally), in six bladder neck pressure, and in six prostate contracton. Each of the 12 HGN stimulations made proximal to the site that had been sutured in dogs that had HGN-HGN reattachment caused responses of the three organs specified above that were comparable to those in control dogs. Manual penile stimulation elicited antegrade ejaculation in all three dogs examined.

CONCLUSIONS

The results of this study show that the function of the HGN in the seminal tract can be preserved after HGN-HGN reattachment and that restoration of its cross-innervation mechanism is possible.

Nerve-sparing retroperitoneal lymph node dissection for metastatic testicular cancer

BACKGROUND

Nerve-sparing techniques are used during retroperitoneal lymph node dissection (RPLND) in patients with early stage testicular cancer to preserve postoperative ejaculatory function. Indications for the procedures have been extended to patients with a postchemotherapy retroperitoneal residual mass without compromising the efficacy of surgery. We report 6 cases diagnosed with metastatic testicular cancer who underwent nerve-sparing RPLND.

METHODS

Between January 1994 and March 1996, 6 patients with metastatic testicular cancer underwent nerve-sparing RPLND. Five of these patients received primary chemotherapy and a retroperitoneal residual mass. Four patients underwent complete bilateral RPLND and 2 underwent unilateral template surgery.

RESULTS

After a mean follow-up of 18.7 months (range, 8 to 34), there have been no local recurrences and 5 (83%) patients report antegrade ejaculation.

CONCLUSION

Nerve-sparing RPLND is applicable for selected patients with metastatic testicular cancer without increasing the risk of local recurrence. Ejaculatory function is preserved in the majority of patients, contributing to the improvement of the quality of life in men who require such surgery.

The urodynamic status during psychogenic erection in a patient with a conus medullaris injury. Case report

The urodynamic status of a 24 year old male patient with psychogenic erection who sustained a conus medullaris lesion from a burst fracture of the first lumbar vertebra is reported. During the initial measurement the external urinary sphincter pressure began to rise from the base pressure of 35 cm H2O 5 seconds after the beginning of audiovisual sexual stimulation and reached the peak of 110 cm H2O. In parallel, the bladder neck pressure gradually rose from its base pressure of 5 cm H2O to a maximal pressure of 115 cm H2O and then ejaculation occurred. The difference is no more than 5 cm H2O and this small difference in pressure inhibits retrograde ejaculation.

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.

A test for the identification of relevant sympathetic nerve fibers during nerve sparing retroperitoneal lymphadenectomy

We present a new intraoperative test for the identification of sympathetic nerve fibers relevant to ejaculation during nerve sparing retroperitoneal lymphadenectomy in patients with nonseminomatous testicular tumors. Electrostimulation of specific isolated postganglionic nerve fibers resulted in intraoperative ejaculation in 9 of 11 patients. Ejaculation was without tumescence in a noneruptive manner and was reproducible in most cases upon repeated stimulation. In 6 patients ejaculation resulted after stimulation of the L3 fiber and in 1 each after stimulation of the L1, L2 and hypogastric plexus. The test seems to be particularly useful in post-chemotherapeutic dissections or otherwise extended dissections when sparing of irrelevant fibers is to be avoided.

A mechanism of retrograde ejaculation after bilateral hypogastric nerve transections in the dog

To pursue the mechanism of retrograde ejaculation after bilateral hypogastric nerve transections, the disability of the lumbosacral sympathetic trunk and the spermatic nerve to compensate bladder neck closure was investigated while both act as compensatory pathways for seminal emission. Five mongrel dogs were used for each experiment. By manual penis-stimulation, all dogs showed only retrograde ejaculation one month and six months after transection of bilateral hypogastric nerves. Bladder neck closure did not occur by electrical stimulation of either the lumbosacral sympathetic trunk or the spermatic nerve before and one month after transection of bilateral hypogastric nerves in all dogs examined and persistent relaxation of bladder neck was observed one and six months after transection of bilateral hypogastric nerves. The present results and our previous data indicate that retrograde ejaculation after bilateral hypogastric nerve transections is attributable to the absence of effective compensatory sympathetic pathways for bladder neck closure under the recovery of seminal emission by compensatory pathways.

Ability of each lumbar splanchnic nerve and disability of thoracic ones to generate seminal emission in the dog

Control of seminal emission by canine thoracolumbar splanchnic nerves which constitute the caudal mesenteric plexus (inferior mesenteric and superior hypogastric plexuses in human) was investigated. Electrical stimulation of a splanchnic nerve group which branched from sympathetic trunks at thoracic and L1 ganglia and descended on the ventral wall of the aorta between bilateral spermatic arteries via the intermesenteric plexus did not cause seminal emission in all 13 dogs examined. In contrast, electrical stimulation of the other splanchnic nerve group which branched from lumbar sympathetic trunks at ganglia L1-L5 and descended behind bilateral spermatic arteries induced seminal emission regardless of branching levels or sides. The results indicate that efferent signals via the intermesenteric plexus do not generate seminal emission, while those via each lumbar splanchnic nerve have ability to generate seminal emission in the dog.

Seminal emission by electrical stimulation of the spermatic nerve and epididymis

The spermatic nerve and epididymis were stimulated electrically in dogs to elucidate the possibility of artificial seminal emission after bilateral transection of the hypogastric nerves and sympathetic trunks. Before transection, electrical stimulation of a distal end of the severed spermatic nerve caused a trace amount of emission in two dogs and no emission in the remaining four. In contrast, 1 month after the transection, stimulation of a distal end of the severed spermatic nerve caused seminal emission in all six dogs examined, with full seminal volume in four dogs and partial volume in the remaining two. Anatomically, sympathetic nerves originating from the upper portion of the lumbar sympathetic ganglia descended along the spermatic arteries to the testes as spermatic nerves. The present results indicate that spermatic nerves have the potential to generate seminal emission as a compensatory pathway after bilateral transection of the hypogastric nerves. Both direct and percutaneous electrical stimulation of epididymal tails resulted in a full volume of seminal emission in all dogs with transection of both hypogastric nerves and lumbosacral sympathetic trunks as well as in unoperated controls, while high voltage (8 V vs 40-80 V) was required to cause seminal emission by electrical stimulation on the skin surface. Direct stimulation of epididymal tails in men undergoing orchidectomy as treatment for prostatic carcinoma or during biopsy of the contralateral testis in a patient with a testicular tumour, resulted in seminal emission in all five epididymides examined either from the end of the severed vas deferens or in the posterior urethra if the vas deferens was not severed.