Objective To study the effects of
carvedilol on
action potentials in guinea pig right ventricular papillary muscles by using
standard microelectrodes technique. Methods The changes in
action potentials of guinea pig papillary muscles and ventricular myocytes were observed after the effect of 0.03,0.30 and 3.00 μmol·L~(-1)
carvedilol in normal and simulated ischemic conditions. Results The results indicated that under the simulated ischemic conditions,the action potential duration(APD) was shortened(P<0.05).When stimulation frequency was set at 1 Hz,0.03,0.30 and(3.00)μmol·L~(-1)carvedilol prolonged APD_(90) 9.0%,10.1% and 18.3%,respectively.Carvedilol caused a concentration-dependent prolongation of action potential duration with gradual return to its original level later.There was no effect on V_(max).But under simulated ischemic conditions,different concentrations of carvedilol could respectively inhibit the shortening of APD induced by ischemia with no effect on V_(max). Conclusion The hypoxia induced shortening of action potential duration in papillary muscle of guinea pigs' ventricle can be inhibited by carvedilol.