Effects of Protopanaxatriol-Ginsenoside Metabolites on Rat N-Methyl-D-Aspartic Acid Receptor-Mediated Ion Currents
Effects of Protopanaxatriol-Ginsenoside Metabolites on Rat N-Methyl-D-Aspartic Acid Receptor-Mediated Ion Currents
- Tae-Joon Shin Sung-Hee Hwang Sun-Hye Choi Byung-Hwan Lee Jiyeon Kang Hyeon-Joong Kim R. Suzanne Zuki
- 대한생리학회-대한약리학회
- The Korean Journal of Physiology & Pharmacology
- 제16권 제2호
- 등재여부 : KCI등재
- 2012.01
- 113 - 118 (6 pages)
Ginsenosides are low molecular weight glycosides found in ginseng that exhibit neuroprotective effects through inhibition of N-methyl-D-aspartic acid (NMDA) receptor channel activity. Ginsenosides, like other natural compounds, are metabolized by gastric juices and intestinal microorganisms to produce ginsenoside metabolites. However, little is known about how ginsenoside metabolites regulate NMDA receptor channel activity. In the present study, we investigated the effects of ginsenoside metabolites, such as compound K (CK), protopanaxadiol (PPD), and protopanaxatriol (PPT), on oocytes that heterologously express the rat NMDA receptor. NMDA receptor-mediated ion current (I<sub>NMDA</sub>) was measured using the 2-electrode voltage clamp technique. In oocytes injected with cRNAs encoding NMDA receptor subunits, PPT, but not CK or PPD, reversibly inhibited I<sub>NMDA</sub> in a concentration-dependent manner. The IC<sub>50</sub> for PPT on I<sub>NMDA</sub> was 48.1±4.6 ՌM, was non-competitive with NMDA, and was independent of the membrane holding potential. These results demonstrate the possibility that PPT interacts with the NMDA receptor, although not at the NMDA binding site, and that the inhibitory effects of PPT on I<sub>NMDA</sub> could be related to ginseng-mediated neuroprotection.