Effects of benzyltetrahydropalmatine on action potentials of myocardium and transmembrane K+ and Ca2+ currents in Purkinje fibers

Standard microelectrode and two-microelectrode voltage clamp techniques were used to study the effects of benzyltetrahydropalmatine (BTHP) on action potentials of isolated myocardium and transmembrane K+ and Ca2+ currents in Purkinje fibers. The effect of BTHP 3-100 mumol/L consisted of prolongation of the action potential duration and reduction of delayed rectifier current (Ik) in concentration-dependent manner. At concentration above 200 mumol/L, the contractile force of the isolated myocardium was depressed and in voltage clamp experiments the slow inward current (Isi) was reduced. These results suggest that the inhibition of Ik induced by BTHP was in relation to its anti-arrhythmic action.