Abstract: The effects of dopexamine(DPX),a new dopamine receptor agonist ,ontransmembrane potential and effective refractory period(ERP)of isolated guinea pig ventricularmuscle superfused either with hypoxia or mimic ischemia perfusates were investigated by usingintracellular microelectrede technique and compared with fenoldopam(FODA) and procaterol.DPX(3 ×10^-6mol·L^-1) was found to significantly reduce both the extent of decrease of resting poten-tial ,action potential amplitude and maximal upstroke velocity and the degree of shortening of actionpotential duration caused by hypoxia or ischemia,These effects of DPX were significantly greater thanthose of FODA and procaterol albeit the latter showed effects similar to DPX,DPX could not onlylengthen the abbreviated ERP resulting from hypoxin,but also shorten the prolonged ERP caused byischemia.This action of DPX was more evident than that of FODA and procaterol.The results revealthe potential advantages of DPX over other dopaminergic agonists in the antiarrhythmic activity duringmvocardial ischemia.