Regenerative component of slow waves in the guinea-pig gastric antrum involves a delayed increase in [Ca2+]i and Cl− channels

Regenerative potentials were initiated by depolarizing short segments of single bundles of circular muscle isolated from the gastric antrum of guinea-pigs. When changes in Ca²⁺]_i and membrane potential were recorded simultaneously, regenerative potentials were found to be associated with an increase in Ca²⁺]_i, with the increase starting after a minimum latency of about 1 s. Although the increase in Ca²⁺]_i was reduced by nifedipine, the amplitudes of the regenerative responses were little changed. Regenerative responses and associated changes in Ca²⁺]_i were abolished by loading the preparations with the Ca²⁺ chelator MAPTA-AM. Regenerative potentials were abolished by 2-aminoethoxydiphenyl borate (2APB), an inhibitor of IP₃ induced Ca²⁺ release, by N -ethylamaleimide (NEM), an alkylating agent which blocks activation of G-proteins and were reduced in amplitude by two agents which block chloride (Cl^?)-selective channels in many tissues. The observations suggest that membrane depolarization triggers IP₃ formation. This causes Ca²⁺ release from intracellular stores which activates Ca²⁺-dependent Cl^? channels.