Plays an important role in the regulation of interdigestive gastrointestinal motility and indirectly causes rhythmic contraction of duodenal and colonic smooth muscle. Present in the gut mucosa with the exception of the gastric corpus. Also present in medulla oblongata, nucleus of the solitary tract, hypophysis, spinal cord, hypothalamus, and cerebellum but not in the cerebral cortex. Belongs to the motilin family.