Central nervous system control of gastrointestinal motility and secretion and modulation of gastrointestinal functions

Abstract

Although the gastrointestinal (GI) tract possesses intrinsic neural plexuses that allow a significant degree of autonomy over GI functions, the central nervous system (CNS) provides extrinsic neural inputs that regulate, modulate, and control these functions. While the intestines are capable of functioning in the absence of extrinsic inputs, the stomach and esophagus are much more dependent upon extrinsic neural inputs, particularly from parasympathetic and sympathetic pathways. The sympathetic nervous system exerts a predominantly inhibitory effect upon GI muscle and provides a tonic inhibitory influence over mucosal secretion while, at the same time, regulates GI blood flow via neurally mediated vasoconstriction. The parasympathetic nervous system, in contrast, exerts both excitatory and inhibitory control over gastric and intestinal tone and motility. Although GI functions are controlled by the autonomic nervous system and occur, by and large, independently of conscious perception, it is clear that the higher CNS centers influence homeostatic control as well as cognitive and behavioral functions. This review will describe the basic neural circuitry of extrinsic inputs to the GI tract as well as the major CNS nuclei that innervate and modulate the activity of these pathways. The role of CNS-centered reflexes in the regulation of GI functions will be discussed as will modulation of these reflexes under both physiological and pathophysiological conditions. Finally, future directions within the field will be discussed in terms of important questions that remain to be resolved and advances in technology that may help provide these answers.

Figure 1

Schematic representation of neuroanatomical connections between the gastrointestinal (GI) tract and central nuclei involved in the regulation of gastrointestinal functions. Note that the location of nuclei is not intended to be anatomically accurate. AP—area postrema; DMV—dorsal motor nucleus of the vagus; NTS—nucleus of the tractus solitarius; PB Complex—parabrachial complex (i.e., parabrachial nucleus + Kölliker-Fuse nucleus); PAG—periaqueductal gray; CeA—central nucleus of the amygdala; Vestibular N—vestibular nucleus; Trigeminal N—trigeminal nucleus; Raphe N—raphe nuclei.

Figure 2

Schematic representation of the neuroanatomical connections between midbrain and forebrain structures involved in the regulation of gastrointestinal (GI) functions. Note that the location of nuclei is not intended to be anatomically accurate. CeA—central nucleus of the amygdala; BNST—bed nucleus of the stria terminals; PAG—periaqueductal gray; LC—locus coeruleus; Barrington’s N—Barrington’s nucleus; PB complex—parabrachial complex (i.e., parabrachial nucleus + Kölliker-Fuse nucleus).