Role of neural and humoral mediators in the gastrocolonic response.

The phenomenon that meal ingestion immediately increases colonic motility was at first referred to as the "gastrocolic reflex", but later changed to the "gastrocolonic response" because of the possible involvement of humoral mediators. This review aims to describe the various mechanisms providing stimuli that alter the gastrocolonic response by dividing it into 'cephalic', 'gastric', and 'intestinal' phases, just as the process of gastric acid secretion after feeding, for a better understanding of the gastrocolonic response. The gastrocolonic response occurs within minutes after feeding and continues for 30-120 min. Fat must be an important component of the ingested meal to induce the gastrocolonic response, but the role of carbohydrates and amino acids remains unclear. The cephalic phase of the gastrocolonic response exists, but the mechanism, including the role of brain-gut peptide ghrelin, remains largely undetermined. Mechanoreceptors and nociceptors of vagal afferents are involved in the gastric phase of GCR. Chemoreceptors in the duodenum play a role in the intestinal phase of GCR. The GCR was not observed in the extrinsically denervated colonic segment. Thus, the involvement of neural factors has been shown in all three "cephalic", "gastric", and "intestinal" phases of the gastrocolonic response. There has been no definitive evidence to show the involvement of humoral factors, but the humoral mechanism cannot be dismissed. The GCR was abnormal or diminished in patients with chronic constipation and diabetes mellitus. These results indicate that neural pathways, rather than humoral pathways, are important mediators of the gastrocolonic response.