Origin and characterization of migrating myoelectric complex in rabbits.

Myoelectric activity patterns of the upper gastrointestinal tract were recorded using chronically implanted electrodes in conscious rabbits. A cyclical pattern of intense spiking activity occurring on almost every slow wave for 10-15 min, corresponding to the regular spiking phase or phase III of the migrating myoelectric complex (MMC), was recorded. This activity was detected by electrodes implanted distal to the ligament of Treitz on the proximal jejunum at a frequency of 9.4-10.6/24 hr. The MMC pattern occurred in both fed and fasted animals, regardless of the presence of cecotrophy. Initiation of phase III activity on the jejunum persisted after transplantation of the pancreatic duct opening to the proximal duodenum 5 cm from the pylorus and when gastric contents emptied directly into the proximal jejunum through a large gastrojejunostomy. It is concluded that the MMC pattern of the rabbit small intestine is persistently initiated in the proximal jejunum distal to the pancreatic and biliary ducts. The jejunal origin of the MMC in the rabbit is reminiscent of that seen transiently 8-10 hr after a meal in dogs during the change from fed to the fasted pattern of gastrointestinal motor activity.