The multiple microelectrode technique of intracellular current application and transmembrane voltage (Vm) recording was employed to study the effects of antiarrhythmic drugs on sheep Purkinje fibers characterized by two levels of steady-state potential. One steady state was at an essentially normal resting potential (Vr) from which a sodium-dependent propagated action potential could be elicited; the other was at a low Vm that followed a failure to reach the threshold for repolarization. In these fibers, no slow response action potential or sustained rhythmic activity could be elicited and no propagated conduction occurred. Intracellularly applied current could shift the Vm from one steady state to the other. The findings include: the demonstration that some Purkinje fibers injured presumptively by ischemia or stretch have two steady states: one at Vr and the other at the plateau potential; the use of intracellular current application for Vm control was useful in identifying such fibers; lidocaine, phenytoin and propranolol could facilitate the attainment of the repolarization threshold with 'normalization' of the action potential resulting in one steady-state potential at Vr and essentially normal impulse propagation when before there was none; procainamide and disopyramide were not observed to have such a normalization effect; and lidocaine, phenytoin, and propranolol in combination with disopyramide could facilitate normal repolarization even when disopyramide alone failed to do so.
|Original language||English (US)|
|Number of pages||9|
|Journal||Journal of Pharmacology and Experimental Therapeutics|
|State||Published - Dec 1 1978|
ASJC Scopus subject areas
- Molecular Medicine