Evidence for a Modulated Receptor Mechanism of Calcium Channel Blockade
A large body of evidence suggests that the action of local anesthetics and antiarrhythmic drugs on membrane sodium channels is modulated by the state of the channel. That is, the affinity of the drug for its receptor varies and depends on whether the channel is rested and available, activated and open (conducting), or closed and inactivated (1–4) (see Fig. 1). The modulated receptor hypothesis for the action of sodium channel blockers has provided explanations for such phenomena as the selective depression of conduction in ischemic myocardium, suppression of tachycardias, and the selective action of lidocaine on ventricular vs. atrial tissue (4).
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