NEUROTOXIC ACTION OF SOME ANTIARRHYTHMIC AGENTS - COMPARATIVE EFFECTSOF PROPAFENONE, LIDOCAINE AND AMIODARONE ON LEECH RETZIUS NERVE-CELL

A series of antiarrhythmic drugs was studied on spontaneous spike acti vity and depolarizing outward potassium current in leech Retzius nerve cells. Propafenone (0.7 mu M/ml) produced a cardiac-like action poten tial with a rapid depolarization followed by a sustained, depolarizati on or plateau, which is terminated after 250 msec by a rapid repolariz ation. The effect of lidocaine (0.7 mu M/ml) on spontaneous spike acti vity was less pronounced, and early afterdepolarization has been recor ded, Amiodarone at the same and much higher concentrations (3 mu M/ml) did not generate either a cardiac-like action potential or an early a fterdepolarization. In the voltage clamp experiments, fast and slow ca lcium-activated outward potassium currents were suppressed with propaf enone and lidocaine but not with amiodarone. These results suggest tha t the antiarrhythmic drugs, propafenone and lidocaine modulate calcium -activated potassium channels in leach Retzius nerve cells.