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.
In many organs, blood flow is maintained at a relatively constant level although pressure changes substantially. This autoregulation of blood flow is achieved in several ways including the myogenic response (MR). MR is triggered by mechanical stretch of vascular smooth muscle. Activation of stretch activated channels (SACs) on vascular smooth muscle cells induces depolarization, Ca2+ influx and myogenic constriction. Non-selective cation channel, epithelial Na+ channel, chloride channel and potassium channel have been suggested as a molecular candidate of SAC. Additionally, activation of protein kinase C (PKC) and Rho-A kinase (ROK) contribute to MR without alteration of intracellular Ca2+. These complex interactions of Ca2+-dependent and Ca2+-sensitizing signals seem to be variable depending on the types of arteries as well as animal species. Finally, impaired MRs are related in various pathological conditions, such as hypertension, stroke and diabetes mellitus. Therefore, identification of MR signaling mechanism might be a target of treatment in vascular diseases.
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