Ventricular automaticity induced by bromobenzoyl-methyladamantylamine (BMA) in different membrane potential ranges in...

The electrophysiological effects of bromobenzoyl - methyladamantylamine ( BMA ) were investigated in isolated electrically driven right ventricular papillary muscles of guinea pigs using conventional glass-microelectrode technique. BMA markedly increased the action potential duration, depolarized the membrane, reduced the maximum rate of depolarization (Vmax) and induced pacemaker-like action potentials. In ventricular myocardium depolarized partially (up to --40 mV) by incubation with 26 mM K+-Krebs solution, BMA induced slow action potentials. In these preparations, BMA was also able to evoke automaticity. Since the pacemaker activity occurring in the voltage range of --90 mV to --60 mV has been attributed to the deactivation of a pacemaker K+ current labelled IK2, and that occurring in the plateau range (from --40 mV to +10 mV) has been attributed to the deactivation of an outward plateau K+ current labelled IX1 , it can be concluded that BMA may inhibit both IK2 and IX1 currents.