Ginsenoside Rg₃ regulates GABAA receptor channel activity: Involvement of interaction with the γ₂ subunit
2013
Lee, Byung-Hwan | Kim, Hyeon-Joong | Chung, Leeyup | Nah, Seung-Yeol
Ginseng exhibits beneficial effects on GABAA receptor-related anxiety and sleep disorders. However, little is known regarding the cellular and molecular bases of the ginseng action on GABAA receptor. The present study was performed to elucidate the molecular mechanism of the ginseng effect on GABAA receptor. The effect of ginsenoside Rg₃ (Rg₃), one of the active ingredients of ginseng, on γ-aminobutyric acid (GABA)A receptor channel activity was examined in Xenopus oocytes using two-electrode voltage-clamp technique. Rg₃ itself evoked an inward current in Xenopus oocytes expressing GABAA receptor subunits (α₁β₁γ₂) and the Rg₃ itself-elicited inward current was only selective to γ₂ subunit expression ratio, since Rg₃ alone had no effects in oocytes expressing other subunits such as γ₁, γ₃, δ, or ε. Co-treatment of Rg₃ with GABA enhanced GABA receptor (α₁β₁γ₂)-mediated inward currents (IGABA) but Rg₃-mediated IGABA enhancement was independent on γ₂. Rg₃ itself-elicited inward current was blocked by GABAA receptor antagonist. The present results indicate that Rg₃-induced GABAA receptor activation via the γ₂ subunit and IGABA enhancement by Rg₃ might be one of the molecular bases of ginseng effects on GABAA receptor.
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