using standard microelectrode techniques , we have measured vmax and conduction velocity in guinea pig papillary muscles exposed to tetrodotoxin and low sodium ( agents expected primarily to decrease , directly , the rapid inward current ) , increased extracellular potassium ( an agent which decreases the rapid inward current at least partially by inactivation mediated by depolarization of the resting membrane potential ) , and , over a wide range of stimulation frequencies , the antiarrhythmic drugs , quinidine , lidocaine , and procainamide .
C0003195
antiarrhythmic drugs
C0034414
quinidine