Inhibitory effects of a bisbenzylisoquinline alkaloid dauricine on HERG potassium channels

Ethnopharmacological relevanceThe roots of Menispermum dauricum have been widely used for the treatment of inflammation, allergy and arrhythmia in China for a long time. Dauricine (Dau), a bisbenzylisoquinline alkaloid from Menispermum dauricum, mainly contributes to the anti-arrhythmic effect and has received pharmacological attention. Dau can prolong the action potential duration (APD), which has been attributed to its ability to modulate Ca2+ and several K+ channels. However, its effects on human-ether-a-go-go-related gene (HERG) channels are unknown.Aim of the studyThe effects of Dau on HERG channels were investigated.Materials and methodsWhole-cell patch-clamp technique was used to record HERG current (IHERG) carried by recombinant HERG channels expressed in HEK293 cells.ResultsDau inhibited IHERG in a concentration-dependent manner with an IC50 of 3.5 μM. Development of block and washout were fast. The inhibitory action of Dau was contingent on channel gating, showing significant voltage and time dependence. Dau inhibited IHERG in the open and inactivated states, but not in the closed states. The activation curve was shifted in a negative direction.ConclusionsDau inhibits HERG encoded potassium channels and this action might be a molecular mechanism for the previously reported APD prolongation with this drug.

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