Effects of countershock-type field stimulation on the electromechanical properties of guinea pig ventricular muscles

The authors investigated the effects of countershock-type electric field stimulation of various intensities on transmembrane action potentials and isometric contraction in isolated guinea pig ventricular muscles. Since increases of developed tension and resting tension were often noted immediately after the field stimulation, it is reasonable to speculate that the stimulation might alter intracellular calcium concentration. Therefore, another purpose of the study was to examine the influences of nifedipine, a potent inhibitor of the voltage dependent calcium channel, and of ryanodine, an inhibitor of the sarcoplasmic reticuulum calcium release. The results have revealed that countershock-type high-intensity electric field stimulation causes prolonged depolarization and spontaneous activity in guinea pig ventricular muscles