Influence of Ischemic-Simulation on the Action Potential Characteristics in Rat Atrial Fibers

Background:To investigate the mechanisms of myocardial ischemia induced changes of electrophysiological properties, influences of various ischemic-simulated Tyrode's solutions on the changes of action potential characteristics were examined. Method:Action potential characteristics were measured during superfusion with various ischemic-simulated solutions (modified physiologic salt solution;MPSS by the method of conventional microelectrode technique in rat atrial fibers. Results:Hypoxic-, hyperkalemic-, and mixed-MPSS decreased ' maximum diastolic potential' (MDP and ' action potential amplitude' (APA, however, no significant changes of MDP and APA were observed by acidic- and glucose-free-MPSS.' Maximum velocity of phase 0 depolariza- tion' (dV/dtmax and ' time for 90% repolarization' (APD90 significantly decreased during hypoxic- and mixed- MPSS superfusion, and hyperkalemic-MPSS also decreased the dV/dtmax and APD90. However, no significant changes in dV/dtmax and APD90 were observed by acidic- and glucose-free-MPSS. The decreasing effects of dV/ dt max and APD 90 by the MPSSes were attenuated when the MPSSes were replaced with normal Tyrode's solution. DPCPX (2×10