The gastrocolic response: Is it gip?

Abstract

Previous experiments demonstrated that feeding is followed by increased electrical spike discharges and contractions of colon smooth muscle. This gastrocolic response has a definite lag period before onset, and is not due to distention of the colon by food. In these experiments, the possible association between altered serum concentration of certain gastrointestinal hormones and the gastrocolic response was investigated in eight stump-tailed monkeys. The animals had extraluminal miniature strain gauge force transducers and bipolar silver electrodes applied in pairs to the serosal surface of the cecum, ascending colon, and transverse colon to record contractions of circular muscle and electrical spike discharge potentials. The serum concentrations of gastrin, cholecystokinin, and gastric inhibitory polypeptide were measured by radioimmunoassay, and the contractile responses of the bowel were recorded, before and after presentation to fasted animals in random order of a dry meal, a wet saline meal, a wet magnesium sulfate meal, or a continued fast. The dry meal was associated with an increase in frequency of electrical spike discharges and contractions of circular colon muscle, as well as an increase in the serum concentration of gastric inhibitory polypeptide, both events occurring 15–60 min after beginning the meal. Other meals had no effect on colon motility or serum gastric inhibitory polypeptide concentration. Serum gastrin and cholecystokinin concentrations were unchanged by all experimental manipulations. This evidence supports our hypothesis that the gastrocolic response has an hormonal basis.