Calcium, calcium channels, and calcium channel antagonists

Voltage-dependent Ca²⁺ channels are an important pathway for Ca²⁺ influx in excitable cells. They also represent an important site of action for a therapeutic group of agents, the Ca²⁺ channel antagonists. These drugs enjoy considerable use in the cardiovascular area including angina, some arrhythmias, hypertension, and peripheral vascular disorders. The voltage-dependent Ca²⁺ channels exist in a number of subclasses characterized by electrophysiologic, permeation, and pharmacologic criteria. The Ca²⁺ channel antagonists, including verapamil, nifedipine, and diltiazem, serve to characterize the L channel class. This channel class has been characterized as a pharmacologic receptor, since it possesses specific drug-binding sites for both antagonists and activators and it is regulated by homologous and heterologous influences. The Ca²⁺ channels of both voltage- and ligand-regulated classes are likely to continue to be major research targets for new drug design and action.