Abstract: In the hypoxic, hyperkalemic and acidosic guinea pig papillary muscles, guanfu base G(GFG) 0.86μmol/L further decreased the maximal rate of depolarization(Vmax) , shortened action potential duration(APD) and effective refractory period(ERP) , and had a significant increase in ERP/APD90 ratio. When the sinoatrial nodes were exposed to GFG, their Vmax , rate of diastolic depolarization, spontaneous firing frequency and mean rate of repolarization were decreased, diastolic interval and APD were prolonged. Furthermore, these effects appear to be concentration-dependent.