Motilin is secreted by endocrine Mo cells (or M cells, these are not the same as the Microfold cells (M cells) that are in Peyer's patches) that are numerous in crypts of the small intestine, especially in the duodenum and jejunum. It is released into the general circulation in humans at about 100-min intervals during the inter-digestive state and is the most important factor in controlling the inter-digestive migrating contractions; and it also stimulates endogenous release of the endocrine pancreas. Based on amino acid sequence, motilin is unrelated to other hormones. Because of its ability to stimulate gastric activity, it was named "motilin". Apart from in humans, the motilin receptor has been identified in the gastrointestinal tracts of pigs, rats, cows, and cats, and in the central nervous system of rabbits.