Direct effects of motilin on isolated smooth muscle from various regions of the human stomach

Abstract

The effects of motilin on gastrointestinal muscles show great variations in different organs and different species. For a precise regional differentiation, we recorded the mechanical activity of longitudinal and circular strips from fundus, corpus and antrum and of circular preparations from the inner and outer layer of the pyloric sphincter and from the duodenum (20 human stomachs). Motilin produced excitatory effects on the mechanical activity of the circular muscle strips from all regions of the human stomach including the pylorus. The effects on longitudinal preparations and on duodenal strips were weak. The most striking effect was an increase of phasic activity (amplitude) in circular antrum preparations, which exceeded the acetylcholine- and bombesin-induced activity. In pylorus preparations, a strong stimulation of phasic activity was observed with a transition to tonic activity in the inner layer of the pyloric ring at high motilin concentrations. The motilin-induced activity of the pyloric preparations was greater than the acetylcholine-induced contractions and even exceeded the bombesin-induced responses in the outer pylorus. The responses of the muscle strips of the proximal stomach (fundus and corpus) were weaker and did not exceed the acetylcholine-induced activity. All effects remained unaltered by atropine and tetrodotoxin application. The study confirms that motilin can interact directly with the smooth muscle of human stomach.

Differential effects of motilin on interdigestive motility of the human gastric antrum, pylorus, small intestine and gallbladder

“…Motilin was demonstrated as an important stimulus for antral phase III in the present study, but appeared not to be a stimulus for phase IIIs of intestinal origin, probably reflecting the lower density of receptors in these parts of the gut 10 . Although human duodenal muscle strips responded to motilin, the response was only weak 34 . This indicates that motilin probably is less important more distally in the gastrointestinal tract.…”

Delayed Gastric Emptying after Pancreaticoduodenectomy: Influence of the Orthotopic Technique of Reconstruction and Intestinal Motilin Receptor Expression

“…Third, gastric atony after PD could occur in response to the reduction of circulating levels of motilin, 11,20,24 a hormone preliminary localized in the mucosa of the duodenum and proximal small intestine. 32,36,37 This point is of major interest, because our study shows for the first time that the density of motilin receptor-positive cells decreases significantly behind the duodenum in aboral direction. Motilin is responsible for stimulating the gastrointestinal motor complex.…”

Translational neuropharmacology: the use of human isolated gastrointestinal tissues

“…This distribution of immunoreactive receptors suggests that the predominant activity of motilin is achieved via receptors on the muscle, and indeed there have been many studies which have examined the abilities of motilin receptor agonists to cause GI muscle contraction (e.g. Lödtke et al, 1989). More recent studies have, however, examined the ability of motilin receptor agonists to facilitate cholinergic activity evoked by EFS in rabbit (Dass et al, 2003;Jarvie et al, 2007;Sanger et al, 2009) and human isolated stomach.…”