Regenerative potentials evoked in circular smooth muscle of the antral region of guinea-pig stomach

1. Slow waves recorded from the circular smooth muscle layer of guinea-pig antrum consisted of two components, an initial component and a secondary re generative component. Whereas both components persisted in the presence of nifedipine, the secondary component was abolished by a low concentration of caffeine. 2. Short segments of single bundles of circular muscle were isolated and im paled with two microelectrodes. Depolarizing currents initiated regenerativ e responses which resembled those initiated during normal slow waves. These responses had partial refractory periods of 20-30 s and were initiated abo ut 1 s after the onset of membrane depolarization. 3. The regenerative responses persisted in the presence of either nifedipin e or cobalt ions but were abolished by caffeine, BAPTA or cyclopiazonic aci d. 4. The observations suggest that depolarizing membrane potential changes tr igger the release of Ca2+ from intracellular stores and this causes a depol arization by activating sets of unidentified ion channels in the membranes of smooth muscle cells of the circular layer of guinea-pig antrum.