EXCITATION-CONTRACTION COUPLING IN GASTRIC MUSCLES

Several mechanisms contribute to the regulation of force generated by gastric muscles. Phasic contractions in the stomach are triggered by the propagation of electrical slow waves. These events are associated with an influx of Ca2+ and an increase in intracellular Ca2+ sufficient to elicit contraction. Entry of Ca2+ may be supplemented by the release of Ca2+ from intracellular stores. Excitatory agonists enhance the amplitude of slow waves, increase the amplitude of Ca2+ transients, and increase the force of phasic contractions. Inhibitory agonists have opposite effects. Excitatory agonists may also enhance release of Ca2+ from stores via the production of IP3. Excitatory and inhibitory agonists may also regulate the sensitivity of the contractile apparatus for Ca2+ and therefore alter the contractile response to a given change in intracellular Ca2+.