Basic Features of The Frequency- and Voltage-Dependent Block By D600 of Calcium Channels in Ventricular Muscle
The Ca-dependent, slow inward current (Isi) is of major importance to the heart since the current is intimately connected with excitation-contraction coupling, sinoatrial rhythm, atrioventricular transmission, and certain patterns of dysrhythmia. A variety of organic agents, of which verapamil and D600 (methoxyverapamil) have been best studied, block Ca channels and thereby reduce Isi in cardiac tissue (1–4). The consequences of this action include a depression of the action potential plateau and contraction in ventricular muscle (3,5) as well as a reduction in the sinus rate and a prolongation of conduction time through the AV node (6).
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