Organization and development of pacemaker of the gastrointestinal tract

Rhythmical depolarization and automatic contractions of smooth musculature of the gastrointestinal tract are a consequence of pacemaker activity of c-Kit-immunoreactive cells of mesenchymal origin—interstitial Cajal cells (ICC) that have a peculiar mechanism of intercellular Ca²⁺ balance, which is controlled by mitochondria. Intermuscular layer cells (ICC-MY) generate pacemaker potentials. Their induced depolarization is enhanced by unitary potentials generated by intracellular population—ICC-IM. Summation of unitary potentials in the tact of the pacemaker ones leads to creation of the second potential of slow waves—plateau potentials. Due to the presence of synapse-like structures, ICC serve messenger of transmission of the enteral nervous system onto the muscle. Long processes and close intercellular contacts similar to tight junction provide conductance and coordination of excitation in the intestinal musculature. Electrical rhythmicity appears in the intestinal muscle at the prenatal development period in parallel with the structural and functional ICC maturation, but establishment of mature rhythm parameters occurs in early postnatal ontogenesis. Features of similarity and difference in organization of control by pacemakers of the heart and musculature of the gastrointestinal tract are discussed.