Effects of a meal and gut hormones on plasma motilin and duodenal motility in dog.

Cyclic increases in the motilin level that coincided with phase III activity of interdigestive myoelectric activity of interdigestive myoelectric activity of the duodenum produced varied plasma motilin concentrations in a fasting dog. Ingestion of a meat meal not only abolished the cyclic increases in motilin concentrations, but also resulted in a significant decrease in the plasma motilin level that was accompanied by phase II-like myoelectric activity of the duodenum, a so-called digestive pattern. Although intravenous gastrin or cholecystokinin octapeptide (CCK-OP) or a combination of gastrin, CCK-OP, and secretin converted the interdigestive myoelectric activity to a digestive pattern, the cyclic increases in plasma motilin levels coulc not be changed by these hormones. This study indicates that a cyclic increase in motilin concentration occurs during the interdigestive period, but not during the digestive period. Instead, a significant decrease occurs. These changes in plasma motilin levels do not appear to be produced by three known gut hormones that are released after ingestion of a meal.