A trace component of ginseng that inhibits Ca2+ channels through a pertussis toxin-sensitive G protein
A crude extract from ginseng root inhibits high threshold, voltage-dependent Ca2+ channels through an unknown receptor linked to a pertussis toxin-sensitive G protein. We now have found the particular compound that seems responsible for the effect: it is a saponin, called ginsenoside Rf (Rf), that i...
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Veröffentlicht in: | Proceedings of the National Academy of Sciences - PNAS 1995-09, Vol.92 (19), p.8739-8743 |
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Zusammenfassung: | A crude extract from ginseng root inhibits high threshold, voltage-dependent Ca2+ channels through an unknown receptor linked to a pertussis toxin-sensitive G protein. We now have found the particular compound that seems responsible for the effect: it is a saponin, called ginsenoside Rf (Rf), that is present in only trace amounts within ginseng. At saturating concentrations, Rf rapidly and reversibly inhibits N-type, and other high-threshold, Ca2+ channels in rat sensory neurons to the same degree as a maximal dose of opioids. The effect is dose-dependent (half maximal inhibition: 40 micromolar) and it is virtually eliminated by pretreatment of the neurons with pertussis toxin, an inhibitor of Go and G, GTP-binding proteins. Other ginseng saponins-ginsenosides Rb1, Rc, Re, and Rg1- caused relatively little inhibition of Ca2+ channels, and lipophilic components of ginseng root had no effect. Antagonists of a variety of neurotransmitter receptors that inhibit Ca2+ channels fail to alter the effect of Rf, raising the possibility that Rf acts through another G protein-linked receptor. Rf also inhibits Ca2+ channels in the hybrid F-11 cell line, which might, therefore, be useful for molecular characterization of the putative receptor for Rf. Because it is not a peptide and it shares important cellular and molecular targets with opioids, Rf might be useful in itself or as a template for designing additional modulators of neuronal Ca2+ channels |
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ISSN: | 0027-8424 1091-6490 |
DOI: | 10.1073/pnas.92.19.8739 |