Enteric Nervous System

David Grundy; Michael Schemann

Disclosures

Curr Opin Gastroenterol. 2006;22(2):102-110. 

In This Article

Abstract and Introduction

Abstract

Purpose of Review: Our aim was to provide a synopsis of how the field of enteric neurobiology has advanced during the past year.
Recent Findings: With such a large number of studies to choose from and given our emphasis in last year's issue on developmental aspects of the enteric nervous system, we have focused on several key themes reflecting the current interest in the way the enteric nervous system is altered in disease.
Summary: The new basic science information gathered during the past year provides insight into pathophysiological processes and will pave the way for improved understanding of both organic and 'functional' gastrointestinal disorders.

Introduction

The enteric nervous system (ENS) is considered to be an independent nervous system that controls and coordinates motility, blood flow and secretion to meet the digestion needs of the individual. It contains an estimated 108 neurons in two major ganglionated plexuses that extend the entire length of the bowel in two major layers: the myenteric plexus between the longitudinal and circular muscles and the submucosal plexuses associated with the mucosal epithelium. Reflex function independent of the central nervous system (CNS) arises because of the coordinated activity in sensory neurons, interneurons, and excitatory and inhibitory motorneurons. The ENS is connected to the CNS, however, by both afferent and efferent pathways. The former are the basis for sensation of gut origin, particularly pain but also non-painful sensations such as fullness, bloating, and nausea while efferent connections provide the parasympathetic and sympathetic innervation that helps control and coordinate the different regions of the gastrointestinal tract with their different regional specialized functions.

The neural mechanisms that coordinate gut function rely on a complex interplay between many neuroactive mediators and their receptors. Progress in the past year has helped our understanding of the neuropharmacology of enteric transmitters, ion channels and receptors responsible for the modulation of neuronal activity and the organization of neurally mediated reflex responses. Studies of the enteric innervation are complicated by both qualitative and quantitative differences in neuronal phenotype that exist between species and which often make it difficult to extrapolate to humans. That is why below we focus attention where possible on recent advances gained from studying human tissues and cells. In this way there have been significant advances that have helped to shed light on the pathogenesis of gut disorders (both organic and functional) and at the same time provided opportunities for novel treatments. Here we describe some of these advances with a focus on changes in reflex function that occur under pathophysiological circumstances, in particular in inflammation, postoperative injury, ageing and irritable bowel syndrome. These studies highlight the link between the ENS and the immune system and may lead to treatments aimed at modulating neuro-immune interaction.

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