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Ginsenosides regulate ligand-gated ion channels from the outside
Byung-Hwan Lee1, Sang Min Jeong, Tal Su Ha
1Research Laboratory for the Study of Ginseng Signal Transduction and Department of Physiology, College of Veterinary Medicine, Konkuk University, Seoul 143-701, Korea.
Molecules and Cells
|September 11, 2004
Summary
Ginsenosides Rg3 and M4, from Panax ginseng, inhibit ion channels. These compounds act from outside the cell membrane, not from within, to regulate channel activity.
Area of Science:
- Neuropharmacology
- Molecular Pharmacology
- Ion Channel Physiology
Background:
- Ginsenosides, active compounds in Panax ginseng, affect the nervous system.
- Ginsenosides modulate ligand-gated ion channels, but their site of action (intracellular vs. extracellular) is unclear due to membrane permeability.
Purpose of the Study:
- To determine the extracellular or intracellular site of action for ginsenoside Rg3 (Rg3) and its metabolite M4 on ligand-gated ion channels.
Main Methods:
- Utilized the Xenopus oocyte gene expression system.
- Measured ligand-gated ion currents using the two-electrode voltage clamp technique.
- Applied Rg3 and M4 extracellularly, intracellularly, and to excised membrane patches.
Main Results:
- Rg3 and M4 inhibited 5-HT3A and a3b4 nACh receptor currents when applied extracellularly, but not intracellularly.
- Rg3 inhibited cGMP-gated ion channel currents when applied extracellularly or to outside-out patches, but not intracellularly or with inside-out patches.
Conclusions:
- Ginsenosides Rg3 and M4 regulate ligand-gated ion channel activity exclusively from the extracellular side of the cell membrane.