Abstract: AIM: To observe the effects of different concentrations of sulpiride (1,3,10,30,100μmol/L) on action potentials of rabbit cardiac purkinje fibers under ischemic conditions, and the effects of sulpiride on fast sodium current (I_Na) of ventricular myocytes in guinea pigs.METHODS: By standard microelectrode technique, the effects of different concentrations (1 -100 μmol/L) sulpiride on action potential parameters (APA ) , the depolarization velocity (V_max) , effective refractory period (ERP) and 90 % action potential duration (APD₉₀) of rabbit cardiac purkinje fibers were observed, in which tissues were perfused by simulated ischemic fluid.Single ventricular myocytes in guinea pigs were isolated with enzymatic dissociation method and the effects of sulpiride on INa of ventricular myocytes were recorded using whole-cell patch clamp technique.RESULTS: The effects of different concentrations of sulpiride on the ischemic cardiac purkinje fibers APA, APD90 had no statistical difference, but the Vmax was decreased.Sulpiride (3 -300μmol/L) inhibited INa in a concentration dependent manner (IC50=10.79 μmol/L, the test potential was-35 mV).Sulpiride (10 μmol/L) reduced the maximum conductance(g_max ) of I_Na, and the activation and inactivation voltage of INa were decreased by 1.91mV,5.22 mV (P<0.01) , respectively, the coincidnece time constant was increased, while the maximum activated current of INa recovered to that before administration.CONCLUSION: Sulpiride could lightly reverse the shortening of action potential in cardiac purkinje fibers induced by ischemia reperfusion.Sulpiride also inhibits INa in a concentration dependent manner.Sulpiride probably affects the inactivated-state of sodium channels.

Key words: sulpiride, action potential, arrhythmia, sodium current