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Noh JH, Choi S, Lee JH, Betz H, Kim JI, Park CS, Lee SM, Nah SY: Effects of ginsenosides on glycine receptor alpha1 channels expressed in Xenopus oocytes. Mol Cells. 2003 Feb 28;15(1):34-9.
Ginsenosides, major active ingredients of Panax ginseng, are known to regulate the excitatory ligand-gated ion channel activity. Recent reports showed that ginsenosides attenuate nicotinic acetylcholine and NMDA receptor channel activity. However, it is not known whether ginsenosides also affect the inhibitory ligand-gated ion channel activity. We investigated the effect of ginsenosides on human glycine alpha1 receptor channel activity expressed in Xenopus oocytes using a two-electrode voltage clamp technique. Treatment of ginsenoside Rf enhances glycine-induced inward peak current (IGly) with dose dependent and reversible manner but ginsenoside Rf itself did not elicit membrane currents. The half-stimulatory concentrations (EC50) of ginsenoside Rf was 49.8 +/- 8.9 microM. Glycine receptor antagonist strychnine completely blocked the inward current elicited by glycine plus ginsenoside Rf. Cl- channel blocker 4,4'-disothiocyanostilbene-2,2'-disulfonic acid (DIDS) also blocked the inward current elicited by glycine plus ginsenoside Rf. We also tested the effect of eight individual ginsenosides (i.e., Rb1, Rb2, Rc, Rd, Re, Rg1, Rg2, and Ro) in addition to ginsenoside Rf. We found that five of them significantly enhanced the inward current induced by glycine with the following order of potency: Rb1 > Rb2 > Rg2 > or = Rc > Rf > Rg1 > Re. These results indicate that ginsenosides might regulate gylcine receptor expressed in Xenopus oocytes and this regulation might be one of the pharmacological actions of Panax ginseng. |
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