Effects of Adenosine and Its Receptor Antagonists on Heart Contractility and Heart Rate of Chinese Toad In Vitro

The effects of adenosine and its selective A1-receptor antagonist DPCPX and none-selective receptor antagonist theophilline on heart contractility and heart rate of Chinese toads were studied by heart perfusion.Adenosine could markedly inhibit heart contractility and heart rate with dose-dependent effect.The saturation effect on contractility showed up when the concentration of adenosine in perfusate was above 50 μmol/L,and arrhythmia occurred or heart-beating stopped when the adenosine concentration was above 100 μmol/L.No obvious effect was observed when the hearts were perfused with theophilline or DPCPX,but both the DPCPX and theophilline obviously antagnized adenosine when mixed with adenosine in the perfusate.The experiment proved that adenosine could also inhibit heart functions of amphibian and this inhibition could be antagonized by DPCPX and theophilline.The results indicated that the effects of adenosine on toads hearts might be mediated by A1-receptors.