Thyrotropin‐Releasing Hormone Potently Modulates Peristaltic Motor Activity of the Guinea Pig Small Intestine

Abstract

Thyrotropin‐releasing hormone (TRH) is present in enteric neurons of the guinea pig intestine, which indicates it may have a role in the control of gut motility. Isolated segments of the guinea pig duodenum‐jejunum and ileum were used to examine the effect of TRH on intestinal peristalsis. The peristaltic waves in the proximal small intestine were triggered at a higher intraluminal pressure and exhibited a higher frequency and a lower amplitude than those in the ileum. TRH (0.3–300 nM) induced a concentration‐related increase in the pressure threshold at which peristaltic waves were elicited and a moderate decrease in the amplitude of the peristaltic waves in both regions. However, while the frequency of the peristaltic waves was increased by the peptide in the ileum, it was diminished by TRH (0.3 and 3 nM) in the duodenum‐jejunum. Since the contractile effect of carbachol on the circular muscle of the duodenum‐jejunum remained unaffected by TRH, it appears that the peptide does not act on the muscle directly but influences peristalsis by acting on enteric neurons. The data further suggest that TRH released from enteric neurons may play a physiologic role in the regulation of propulsive motor activity of the gut.