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The Pharmaceutical Society of Korea (대한약학회)
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Effects of Ginsenosides on $GABA_A$ Receptor Channels Expressed in Xenopus Oocytes

  • Choi, Se-Eun (Department of Physiology, College of Veterinary Medicine Konkuk University) ;
  • Choi, Seok (Department of Physiology, College of Veterinary Medicine Konkuk University) ;
  • Lee, Jun-Ho (Department of Physiology, College of Veterinary Medicine Konkuk University) ;
  • Paul J.Whiting (Merck Sharp ＆ Dohme Research Lab., Neuroscience Research Center) ;
  • Lee, Sang-Mok (Department of Physiology, College of Veterinary Medicine Konkuk University) ;
  • Nah, Seung-Yeol (Department of Physiology, College of Veterinary Medicine Konkuk University)
  • Published : 2003.01.01
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Abstract

Ginsenosides, major active ingredients of Panax ginseng, are known to regulate excitatory ligand-gated ion channel activity such as nicotinic acetylcholine and NMDA receptor channel activity. However, it is not known whether ginsenosides affect inhibitory ligand-gated ion channel activity. We investigated the effect of ginsenosides on human recombinant $GABA_A$ receptor (${\alpha}_1{\beta}_1{\gamma}_{2s}$) channel activity expressed in Xenopus oocytes using a two-electrode voltage-clamp technique. Among the eight individual ginsenosides examined, namely, $Rb_1$, $Rb_2$, Rc, Rd, Re, Rf, $Rg_1$ and $Rg_2$, we found that Rc most potently enhanced the GABA-induced inward peak current ($I_{GABA}$). Ginsenoside Rc alone induced an inward membrane current in certain batches of oocytes expressing the $GABA_A$ receptor. The effect of ginsenoside Rc on $I_{GABA}$ was both dose-dependent and reversible. The half-stimulatory concentration ($EC_{50}$) of ginsenoside Rc was 53.2$\pm$12.3 $\mu$M. Both bicuculline, a $GABA_A$ receptor antagonist, and picrotoxin, a $GABA_A$ channel blocker, blocked the stimulatory effect of ginsenoside Rc on $I_{GABA}$. Niflumic acid (NFA) and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), both $CI^{-1}$ channel blockers, attenuated the effect of ginsenoside Rc on I$I_{GABA}$. This study suggests that ginsenosides regulated $GABA_A$ receptor expressed in Xenopus oocytes and implies that this regulation might be one of the pharmacological actions of Panax ginseng.

Keywords

References

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