ObjectiveTo investigate effect of isoproterenol on spontaneous rhythm and INCX in newborn rat’s sino-atrial node cell.MethodsThe sino-atrial node cells of newborn Wistar rats were enzymatically disassociated by the method of enzyme digestion with differential attachment．Whole-cell patch clamp technique was used to record INCX.ResultsThe spontaneous rhythm in sino-atrial node cells was significantly enhanced by ISO 1.0 μmmo/L.INCX was larger after exposure to ISO in voltage- and concentration-dependent fashion.At +80mV of test potential, outward current densities of INCX were increased from (0.52±0.03) pA/pF to (0.72±0.04) pA/pF (n=10，P<0.05), meanwhile, inward current densities of INCX at -120 mV were increased from (-3.26±0.02) pA/pF to (-7.81±0.06) pA/pF (n=10，P<0.01).ConclusionINCX participates in the sino-atrial node automatically depolarization in newborn rat’s sino-atrial node cells, which is regulated by ISO.