| Abstract: | Rhythmical depolarization and automatic contraction of smooth muscle of the gastrointestinal tract are consequences of pacemaker activity of c-Kit-immunoreactive cells of mesenchymal origin--interstitial Cajal cells (CC) that have a peculiar mechanism of intracellular Ca2+ exchange controlled by mitochondria. The intermuscular layer cells (ICC-MY) generate pacemaker potentials. They produce depolarization that is enhanced by unitary potentials evoked by the intermuscular population--ICC-IM. Summation of unitary potentials in time of the pacemaker ones leads to creation of the second potentials of slow waves--plateau-potentials. Due to the presence of synapse-like structures, ICC serve messengers of transmission of signals of the enteral nervous system to muscle. Long processes and tight intercellular contacts similar to the cleft ones provide transduction and coordination of excitation in the intestinal musculature. Electrical rhythmicity appears in the enteric musculature at the prenatal period in parallel with structural and functional ICC maturation, but formation of mature rhythm parameters occurs in postnatal ontogenesis. Features of similarity and differences in organization of control of heart and the gastrointestinal tract musculature by pacemakers are considered. |
