Effects of ginsenoside Rg(2) on the 5-HT3A receptor-mediated ion current in Xenopus oocytes

Abstract

Treatment of ginsenosides, major active ingredients of Panax ginseng, produces a variety of pharmacological or physiological responses with effects on the central and peripheral nervous systems. Recent reports showed that ginsenoside Rg(2) inhibits nicotinic acetylcholine receptor-mediated Na+ influx and channel activity. In the present study, we investigated the effect of ginsenoside Rg(2) on human 5-hydroxytryptamine(3A) (5-HT3A) receptor channel activity, which is also one of the ligand-gated ion channel families. The 5-HT3A receptor was expressed in Xenopus oocytes, and the current was measured using the two-electrode voltage clamp technique. The ginsenoside Rg(2) itself had no effect on the oocytes that were injected with H2O as well as on the oocytes that were injected with the 5-HT3A receptor cRNA. In the oocytes that were injected with the 5-HT3A receptor cRNA, the pretreatment of ginsenoside Rg(2) inhibited the 5-HT-induced inward peak current (I-5-(HT)). The inhibitory effect of ginsenoside Rg(2) on I5-HT was dose dependent and reversible. The half-inhibitory concentrations (IC50) of ginsenoside Rg(2) was 22.3 +/- 4.6 muM. The inhibition of I5-HT by ginsenoside Rg(2) was non-competitive and voltage-independent. These results indicate that ginsenoside Rg(2) might regulate the 5-HT3A receptors that are expressed in Xenopus oocytes. Further, this regulation on the ligand-gated ion channel activity by ginsenosides might be one of the pharmacological actions on Panax ginseng.