[Motilin-range and analysis of its action]

Motilin is a polypeptide containing 22 amino-acids from the entero-chromaffin cells of the mucosa of the small intestine. Synthetic analogues (13-norleucine-motilin; 13-leucine-motilin) proved to be equal to the natural polypeptide in the biological aspects. Motilin primarily stimulates the motility of the upper gastrointestinal tract but inhibits gastrin evacuation. The contractile action of motilin does not take place by way of the nerves but through receptors on or in the smooth muscle cell itself. Motilin and cyclic adenosine-3':5'-monophosphate are functional antagonists in the contraction of the gastrointestinal musculature. Depending on the dosis, motilin increases gastric pepsin secretion and inhibits protein biosynthesis in the gastric mucosa itself. Radioimmunological motilin tests will help to determine which of the above-mentioned motilin actions are "physiological" and which of them merely "pharmacological".