Novel electropharmacological activity of amiodarone on human HCN channels heterologously expressed in the Xenopus oocytes

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels underlie the pacemaker currents (If) in cardiac cells. The objectives of this study were to investigate the electropharmacological activity of amiodarone on human HCN channels heterologously expressed in Xenopus laevis oocytes. hHCN channels were expressed in oocytes and studied using the standard two-electrode voltage-clamp techniques. The results show that amiodarone blocks hHCN channels heterologously expressed in the Xenopus oocytes in a concentration- and use-dependent manner, but doesn't modify the voltage dependence of activation and reversal potentials. And the removal of blockage of HCN channels by amiodarone was favored by inward current flow, not by hyperpolarizing potential. Characteristics of blockage on hHCN channels were consistent with those of amiodarone as “trapped” drugs on human ether-a-go-go-related gene (HERG) channels. These results will be useful for elucidating the potentially antiarrhythmic mechanism of amiodarone.