RECENT STUDIES ON REGULATION OF GASTRIC-MOTILITY IN TURKEYS

Recent studies have been aimed at determining how gastroduodenal contractions are initiated and at regulation of the stomach during the intestinal phase of gastric regulation. Intrinsic, myogenic, electrical slow waves, the principal regulators of motility in the mammalian gut, have not been found in the avian gut. Instead, contractions appear to be initiated by a neurogenic pacemaker located between the gastric isthmus and the pylorus. Pacemaker impulses travel over the myenteric plexus to the glandular stomach and the duodenum, and to the muscles of the muscular stomach to initiate contractions. Extrinsic innervation does not appear to be involved in this initiation. The role of two hormones, avian pancreatic polypeptide (aPP) and cholecystokinin (CCK), in regulation of gastric motility has been examined. Both hormones are released postprandially by the presence of ingesta in the upper small intestine and both depress gastroduodenal motility when administered to fowl. Thus, aPP and CCK slow gastric emptying to allow more time for intestinal digestion.