Multiparity affects conduction properties of pelvic floor nerves in rabbits.

Francisco Castelán,Suelem Moreno‐Pérez,Dora L. Corona‐Quintanilla,René Zempoalteca,Kenia López‐García,Margarita Martínez‐Gómez,Mario I. Romero‐Ortega,Ismael Jiménez‐Estrada

doi:10.1002/brb3.1105

Abstract

IntroductionWomen often develop pelvic floor dysfunction due to damage to the pelvic musculature during childbirth; however, the effect on pelvic floor nerves function is less understood. This study used adult rabbits to evaluate the electrophysiological and histological characteristics of the bulbospongiosus (Bsn) and pubococcygeus nerves (Pcn) in multiparity.MethodsCompound nerve action potentials (CNAP) were compared between age‐matched nulliparous and multiparous animals and associated to the histological characteristics of myelinated axons from the Bsn and Pcn nerves. The extensor digitorum longus nerve (EDLn) was used as negative control. Data were analyzed with unpaired two‐tailed Student's t test or Mann–Whitney U test to determine significant differences between groups.ResultsThe onset and peak latencies, duration, and conduction velocity of the motor fibers in these pelvic nerves were not significantly different between nulliparous and multiparous animals. However, the peak‐to‐peak amplitude and area of the CNAP in both Bsn and Pcn were reduced in multiparous rabbits. Histology showed a higher percentage of axons with myelin disorganization caused by multiparity in these pelvic nerves. Together, the data indicate a reduction in the number of functional pelvic axons due to multiparity. As expected, no effect of parity was observed in the EDLn controls.ConclusionsPresent findings demonstrated that multiparity affects myelination and consequently conduction properties in the small pelvic floor nerves.

Highlights

Women often develop pelvic floor dysfunction due to damage to the pelvic musculature during childbirth; the effect on pelvic floor nerves func‐ tion is less understood
We have previously shown that the bulbos‐ pongiosus (Bsm, perineal) and pubococcygeus (Pcm, pelvic) muscles have antagonistic roles during micturition, as the Bsm contracts re‐ flexively during the voiding while the Pcm is activated during the storage phase of micturition (Corona‐Quintanilla et al, 2009)
Present findings demonstrate that multiparity significantly de‐ creased the amplitude and area of the Compound nerve action potentials (CNAP) evoked in the pelvic Bsn and pubococcygeus nerves (Pcn) motor nerves

Summary

| INTRODUCTION

Pelvic floor muscles play a critical role in reproductive and excre‐ tory processes. Women are more prone than men to the onset of pelvic floor dysfunctions as the pelvic floor is more drastically impacted by pregnancy. We have previously shown that the bulbos‐ pongiosus (Bsm, perineal) and pubococcygeus (Pcm, pelvic) muscles have antagonistic roles during micturition, as the Bsm contracts re‐ flexively during the voiding while the Pcm is activated during the storage phase of micturition (Corona‐Quintanilla et al, 2009) These muscles are innervated by the bulbospongiosus (Bsn) and pubococ‐ cygeus nerves (Pcn) and are relatively smaller compared to the pu‐ dendal nerve (Cruz et al, 2017). The anatomi‐ cal location of Bsn and Pcn makes them susceptible to injuries due to pregnancy and childbirth, as indicated by the reportedly altered viscerosomatic reflexes, muscle injury, and impaired mus‐ cle contractility in multiparous rabbits (López‐García et al, 2016; López‐Juárez et al, 2018; Martínez‐Gómez et al, 2011) These al‐ terations could be directly or indirectly related to deficiencies in the functional and anatomical properties of the pelvic and perineal innervation. The study confirmed the damage of the pelvic nerves due to multiparity

| MATERIAL AND METHODS

| DISCUSSION

Findings

CONFLICT OF INTEREST