Fig 5. Working hypothesis of stimulation of acid secretion by motilin in suncus.
In the duodenum, motilin is secreted by the MO cell during the interdigestive state. It was hypothesized that motilin may directly stimulate histamine release through GPR38 expressed on the ECL cell. Another possibility is the indirect pathway, which is either central or peripheral neural stimulation of motilin for histamine release. Finally, the histamine induced by motilin acts on the parietal cell through the H2 receptor to release gastric acid. CCKB and muscarinic cholinergic receptors were not found to be involved in motilin-induced gastric acid secretion. MO cell: motilin-producing cell; GPR38: G-protein coupled receptor 38; CCK: cholecystokinin; CCKBR: cholecystokinin B receptor; ECL cell: enterochromaffin-like cell; ACh: Acetylcholine.