Electrical events underlying organized myogenic contractions of the guinea pig stomach

The stomach generates a characteristic pattern of coordinated activity whereby rings of contraction regularly start in the corpus and migrate slowly down the stomach to the duodenum. This behaviour persists after isolating the stomach and after blocking nervous activity; hence the response is myogenic, resulting from organized contractions of smooth muscle cells lying in the stomach wall. Each ring of contraction is triggered by a long lasting wave of depolarization, termed a slow wave. Slow waves are now known to be generated by sets of interstitial cells of Cajal (ICC), which intermingle with gastric smooth muscle cells. This article describes some studies which identify the roles played by ICC in the on-going generation of coordinated gastric movements. Intramuscular ICC in the corpus generate slow waves and these provide the dominant pacemaker frequency in the stomach. Corporal slow waves, in turn, activate a network of myenteric ICC, which starts in the antrum and slowly conducts waves of depolarization down the stomach. As these waves pass over bundles of circularly orientated muscle cells, they activate a set of intramuscular ICC which lie in the circular muscle layer: these generate slow waves that rapidly spread radially, so triggering each ring of contraction.