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Changes in transmembrane potentials of cardiac ventricular fibers during the early stage of acute cardiac ischemia and protective effects of vagal stimulation in rabbits

Wang Yunxiang, Jin Jiabu, Wang Fuzhou

Department of Physiology, Fourth military Medical College

Abstract

This study was carried out on rabbit hearts. Floating glass microelectrode was used to record the transmembrane potentials of cardiac ventricular fibers in situ. Resting potential (RP), action potential amplitude (APA) and maximum upstroke velocity of phase 0 (dv/dt)_(max) were decreased (P<0.01) 1-5 min after coronary occlusion. The duration of action potential, especially the time required for 30% and 50% of recovery (APD_(30), APD_(50)), was shortened, and the duration of the plateau was shortened even more markedly. These changes in potentials of the ventricular cells during acute ischemia were abolished by vagal stimulation, RP, APA, and (dv/dt)_(max) were increased (P<0.01). Vagal stimulation lengthened APD_(30), APD_(50) and APD_(90) under condition of natural heart rate, it was suggested that the lengthening of the APD during vagal stimulation was due to the decrease in heart rate. These results suggested that recovery of the transmembrane potentials of the ischemic ventricular cells during vagal stimulation was beneficial to impulse conduction in the ventricular muscles and to lengthening of the effective refractory period, which might play an important role in prevention of ventricular arrhythmia in early stage of acute ischemia.

Key words: Floating glass microelectrode;Myocardial transmembrane potential;Acute myocardial ischemia;Vagal stimulation

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Citing This Article：

Wang Yunxiang, Jin Jiabu, Wang Fuzhou. Changes in transmembrane potentials of cardiac ventricular fibers during the early stage of acute cardiac ischemia and protective effects of vagal stimulation in rabbits. Acta Physiol Sin 1986; 38 (3): (in Chinese with English abstract).