Parasympathetic nerve (colon)

Parasympathetic nerves in the colon consist of preganglionic fibers (from the sacral spinal cord S2–S4 and the vagus nerve, depending on the region) that project to ganglia in the pelvic plexus or directly to the enteric (myenteric and submucosal) plexuses of the colon. They mediate the "rest-and-digest" functions by promoting colonic motility, contraction of the rectum, and relaxation of the internal anal sphincter to facilitate defecation. In the rectosigmoid and rectal regions, prominent bundles known as "ascending nerves" or "shunt fascicles" represent parasympathetic input, which can be reliably distinguished via markers such as GLUT1 and neurofilament-H in humans[1]. These nerves are functionally essential for coordinated colonic motility, and injury to these pathways results in impaired bowel function, particularly constipation or impaired defecation[7][9][11]. Parasympathetic control plays a critical role in the neural regulation of the gastrointestinal tract, but as integrated anatomical entities rather than molecular drug targets. Pharmacological interventions affecting bowel motility typically target the downstream neurotransmitter receptors (such as muscarinic receptors) rather than the nerves themselves[3][14]. Key Note: This entry is not a molecular target in the conventional sense (i.e., single receptor, enzyme, ion channel, etc.), but a population of nerve fibers with physiological function. If a molecular target mediating the effects of these nerves is of interest, muscarinic acetylcholine receptors (e.g., M3) would be the more appropriate canonical molecular target.

Other names

Parasympathetic fibers (colon)Sacral parasympathetic nerves (colon)Pelvic nerves (colon)Ascending nerves (colon)

Enhancement or inhibition of neurotransmission to regulate bowel motility (e.g., cholinergic drugs act downstream at muscarinic acetylcholine receptors)