Effects of CS-611 on the electrophysiological properties of canine cardiac tissues

Effects of CS-611, a new coronary vasodilator, on the electrophysiological properties of Purkinje fibers, auricular and ventricular muscles isolated from dogs were examined with a microelectrodfe technique. CS-611 between 3 X 10(-6) and 3 X 10(-5) g/ml shortened the action potential duration (APD) of each tissue, especially of Purkinje fibers, without any significant alterations in the resting membrane potential, action potential amplitude and maximum rate of rise (V max). CS-611 also shortened the effective refractory period (ERP) of Purkinje fibers and ventricular muscles, but to a lesser extent than APD, resulting in an increase of ERP/ADP. The level of membrane potential needed to elicit premature excitation in Purkinje fibers and Vmax of the earliest response tended to increase in the presence of CS-611. CS-611 partially restored the reduced Vmax of Purkinje fibers exposed to hypoxia. The spontaneous firings in Purkinje fibers were decreased or abolished by CS-611. The possible role of these effects of CS-611 in its antiarrhythmic action was discussed.