Motilin is a 22-amino-acid peptide secreted by endocrinocytes in the mucosa of the proximal small intestine. Motilin is a gastrointestinal regulatory polypeptide produced by motilin cells in the duodenal epithelium. Motilin is an intestinal peptide that stimulates contraction of gut smooth muscle. The motilin receptor has not been cloned yet, but motilin-receptor agonists appear to be potent prokinetic agents for the treatment of dysmotility disorders. The nucleic classic sequence for human motilin shows seven differences between it and the cDNA coding for pig motilin, but the amino acid sequence deduced from both sequences is identical.