GLP-1, a hormone, can reduce migrating motor complexes (MMCs) in healthy subjects and IBS patients. In healthy subjects, it reduced MMCs from 2 to 0.5 and motility index from 4.9 to 4.3 ln P (mmHg*s min)1). In IBS patients, it reduced MMCs from 2.5 to 1 without affecting the motility index. At 2.5 pmol kg)1 min)-1, it decreased MMCs from 2 to 1 and the motility index. Motility responses were similar in both the antrum and duodenum. This evidence concerns the gene GLP1R and irritable bowel syndrome.