The gastrocolic reflex or gastrocolic response is one of a number of physiological reflexes controlling the motility, or peristalsis, of the gastrointestinal tract. It involves an increase in motility of the colon in response to stretch in the stomach and byproducts of digestion in the small intestine. The small intestine also shows a similar motility response.
The reflex was demonstrated by myoelectric recordings in the colons of animals and humans, which showed an increase in electrical activity within as little as 15 minutes after eating. The recordings also demonstrated that the gastrocolic reflex is uneven in its distribution throughout the colon. The sigmoid colon is more greatly affected than the right side of the colon in terms of a phasic response; however, the tonic response across the colon is uncertain. A number of neuropeptides have been proposed as mediators of the gastrocolic reflex. These include serotonin, neurotensin, cholecystokinin (CCK), and gastrin.
Clinically, the gastrocolic reflex has been implicated in pathogenesis of irritable bowel syndrome. Also, the serotonin (5HT3) antagonist ondansetron decreases the tonic response to stretch.