Quercetin inhibits α3β4 nicotinic acetylcholine receptor-mediated ion currents expressed in Xenopus oocytes

Abstract

Quercetin mainly exists in the skin of colored fruits and vegetables as one of flavonoids. Recent studies show that quercetin, like other flavonoids, has diverse pharmacological actions. However, relatively little is known about quercetin effects in the regulations of ligand-gated ion channels. In the previous reports, we have shown that quercetin regulates subsets of homomeric ligand-gated ion channels such as glycine, 5-HT3A and α 7 nicotinic acetylcholine receptors. In the present study, we examined quercetin effects on heteromeric neuronal α 3 β 4 nicotinic acetylcholine receptor channel activity expressed in Xenopus oocytes after injection of cRNA encoding bovine neuronal α 3 and β 4 subunits. Treatment with acetylcholine elicited an inward peak current (IACh) in oocytes expressing α 3 β 4 nicotinic acetylcholine receptor. Co-treatment with quercetin and acetylcholine inhibited IACh in oocytes expressing α 3 β 4 nicotinic acetylcholine receptors. The inhibition of I ACh by quercetin was reversible and concentration-dependent. The half-inhibitory concentration (IC50) of quercetin was 14.9± 0.8 μ M in oocytes expressing α 3 β 4 nicotinic acetylcholine receptor. The inhibition of IACh by quercetin was voltage-independent and non-competitive. These results indicate that quercetin might regulate α 3 β 4 nicotinic acetylcholine receptor and this regulation might be one of the pharmacological actions of quercetin in nervous systems.