The functional role of intramuscular interstitial cells of Cajal in the stomach

Intramuscular interstitial cells of Cajal (ICC-IM) are found within the smooth muscle layers of the stomach. ICC-IM are mainly spindle shaped cells with bipolar processes orientated along the long axis of surrounding smooth muscle cells. ICC-IM make close contacts with nerve varicosities and form gap junctions with neighbouring smooth muscle cells, indicating that ICC-IM mediate enteric motor neurotransmission. These morphological properties of ICC-IM are similar throughout the stomach. However, the electrical properties of these cells differ from region to region. In the fundus, ICC-IM generate spontaneous transient depolarizations (STDs), resulting in an ongoing discharge of unitary potentials in the smooth muscle cells. ICC-IM in the corpus generate slow waves and as they fire at the highest frequency they serve as the dominant pacemaker cells in the stomach. On the other hand, ICC-IM in the antrum generate the secondary component of slow waves triggered by the initial component that propagates passively from myenteric ICC (ICC-MY). Thus, the different electrical properties of ICC-IM play a critical role in creating the distinct functions of the proximal and distal regions of the stomach such that the fundus acts as a reservoir of food, the corpus as a dominant pacemaker region, while the antrum acts as a region for mixing and propulsion of food.