OXIME DEPRESSION OF THE FAST SODIUM CURRENT IN MYOCARDIAL-CELLS

Effects of diacetyl monoxime on the fast Na+ current were examined by the whole-cell voltage-clamp method in embryonic chick ventricular myo cytes. Diacetyl monoxime (10-20 mM) decreased the duration and amplitu de of the action potential and depressed the amplitude of the peak fas t inward Naf current by about 25 (10 mM)-45 % (20 mM), without affecti ng other I-V parameters. Neither the activation and inactivation kinet ics of the Na+ channels, such as the time to peak current and the time constant of inactivation, nor the steady state characteristics of the inactivation and activation were affected by diacetyl monoxime. It al so did not alter the window conductance and the recovery kinetics from inactivation (reactivation). Hence, diacetyl monoxime suppresses the fast Nat current, without affecting the time-dependent and voltage-dep endent kinetics.