Site-dependent differences in the composite fibers of male pelvic plexus branches: an immunohistochemical analysis of donated elderly cadavers

Kuniyasu Muraoka,Gen Murakami,Keisuke Hieda,Shuichi Morizane,Atsushi Takenaka,Masashi Honda,Takehiro Sejima,Shin-Ichi Abe

doi:10.1186/s12894-018-0369-9

Kuniyasu Muraoka, Gen Murakami + Show 6 more

Open Access

https://doi.org/10.1186/s12894-018-0369-9

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Abstract

BackgroundAlthough the pelvic autonomic plexus branches are considered to be a mixture of sympathetic and parasympathetic nerves, little is known regarding the composite fibers of the pelvic plexus branches. This study aimed to investigate the immunohistochemical features of sympathetic and parasympathetic nerves in the pelvic autonomic plexus branches.MethodsUsing 10 donated elderly male cadavers, the detailed topohistology of nerve fibers at and around the bladder, seminal vesicle, prostate, and rectum was examined. Neuronal nitric oxide synthase (nNOS) and vasoactive intestinal polypeptide (VIP) were used as parasympathetic nerve markers; tyrosine hydroxylase (TH) was used as a sympathetic nerve marker. The myenteric plexus of the colon was utilized as a positive control.ResultsMost nerve fibers in the bladder, seminal vesicle, prostate, and rectum were both nNOS- and TH-positive. Thus, pelvic plexus branches were classified into two types: 1) triple-positive mixed nerves (nNOS+, VIP+, TH+, thick myelinated fibers + or -) and 2) double-positive mixed nerves (nNOS+, VIP-, TH+, thick myelinated fibers + or -). Notably, triple-positive nerves were localized within the posterosuperior part of the plexus (near the rectum) and travelled anteroinferiorly toward the posterolateral corner of the prostate. The posteriorly and inferiorly located nerves were predominantly composed of parasympathetic, rather than sympathetic, fibers. In contrast, nerve fibers within and along the bladder and seminal vesicle contained either no or few VIP-positive nerves. These superiorly located nerves were characterized by clear sympathetic nerve dominance.ConclusionsThe nerves of the pelvic plexus branches were clearly classified into nerves around the bladder and seminal vesicle (VIP-negative) and nerves around the prostate (VIP-positive). Although nNOS- and VIP-positive nerve fibers are candidate cavernous nerves, cavernous nerve identity cannot be definitively concluded for these nerves in the periprostatic region.

Highlights

The pelvic autonomic plexus branches are considered to be a mixture of sympathetic and parasympathetic nerves, little is known regarding the composite fibers of the pelvic plexus branches
The pelvic plexus branches were classified into two types: 1) triple-positive mixed nerves; and, 2) double-positive mixed nerves
This study focused on the pelvic plexus branches, from the lateral site of the bladder, seminal vesicle, and rectum, to the posteroinferior site at and along the posterolateral corner of the prostate, in elderly male cadavers

Summary

Introduction

The pelvic autonomic plexus branches are considered to be a mixture of sympathetic and parasympathetic nerves, little is known regarding the composite fibers of the pelvic plexus branches. This study aimed to investigate the immunohistochemical features of sympathetic and parasympathetic nerves in the pelvic autonomic plexus branches. The genital organs and lower urinary tract are controlled by the autonomic nervous system, as well as the somatic nerves. Because functional disruptions, such as urinary incontinence and sexual dysfunction, represent important determinants of quality of life, detailed anatomical studies of the pelvic neuroanatomy are essential to preserve continence, erection, and bladder function after pelvic surgery [3, 4]. Recent reports have demonstrated that, in the human pelvic floor, a portion of the pelvic plexus branches contained VIP-, nNOS-, and TH-positive nerve fibers [9,10,11]

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