Abstract: AIM:To study the protective effect of piperine on the abnormalities of action potential duration and L-type calcium current (ICa,L) induced by hydrogen peroxide in single rabbit atrial myocyte. METHODS: Whole-cell patch clamp technique was used to study the effect of H2O2 (10 and 50 μmol/L) on APD and ICa,L in single rabbit atrial myocyte and the effect of pretreatment with piperine (7 μmol/L). RESULTS: Piperine (7 μmol/L) had no significant effect on APD and ICa,L of normal single rabbit atrial myocyte as well as its channel dynamics. In the presence of 10 and 50 μmol/L H2O2, APD50 and APD90 decreased (P<0.05), amplitude of RMP disincreased (P<0.05), the peak of ICa,L was significantly reduced (P<0.05), I-V curve shifted upward, steady-state activation curve of ICa,L was shifted to positive potentials, and steady-state inactivation was shifted to negative potentials, but recovery from inactivation of ICa,L showed no remarkable changes. Piperine (7 μmol/L) significantly alleviated the inhibitory effect of H2O2 on APD and ICa,L (P<0.01) and protected the changes of ICa,L dynamics induced by H2O2. CONCLUSION: Piperine can alleviate abnormalities of APD and ICa,L induced by hydrogen peroxide in atrial myocytes.