Effects of ginsenoside Rg2 on the 5-HT3A receptor-mediated ion current in Xenopus oocytes.
Treatment with ginsenosides, major active ingredients of Panax ginseng, produces a variety of pharmacological or physiological responses with effects on the central and peripheral nervous systems. Recent reports showed that ginsenoside Rg2 inhibits nicotinic acetylcholine receptor-mediated Na+ influx and channel activity. In the present study, we investigated the effect of ginsenoside Rg2 on human 5-hydroxytryptamine3A (5-HT3A) receptor channel activity, which is also one of the ligand-gated ion channel families. The 5-HT3A receptor was expressed in Xenopus oocytes, and the current was measured using the two-electrode voltage clamp technique. The ginsenoside Rg2 itself had no effect on the oocytes that were injected with H2O as well as on the oocytes that were injected with the 5-HT3A receptor cRNA. In the oocytes that were injected with the 5-HT3A receptor cRNA, the pretreatment of ginsenoside Rg2 inhibited the 5-HT-induced inward peak current (I5-HT) The inhibitory effect of ginsenoside Rg2 on I5-HT was dose dependent and reversible. The half-inhibitory concentrations (IC50) of ginsenoside Rg2 was 22.3 +/- 4.6 microM. The inhibition of I5-HT by ginsenoside Rg2 was non-competitive and voltage-independent. These results indicate that ginsenoside Rg2 might regulate the 5-HT3A receptors that are expressed in Xenopus oocytes. Further, this regulation on the ligand-gated ion channel activity by ginsenosides might be one of the pharmacological actions of Panax ginseng.
Choi
Seok
S
Research Laboratory for the Study of Ginseng Signal Transduction, Department of Physiology, College of Veterinary Medicine, Konkuk University, Seoul 143-701, Korea.
Lee
Jun-Ho
JH
Oh
Seikwan
S
Rhim
Hyewhon
H
Lee
Sang-Mok
SM
Nah
Seung-Yeol
SY
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D036145:Ginsenosides / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D008845:Microinjections; D015394:Molecular Structure; D009865:Oocytes; D005894:Panax / Q000737:chemistry; D018408:Patch-Clamp Techniques; D018075:RNA, Complementary / Q000235:genetics; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000235:genetics; D044406:Receptors, Serotonin, 5-HT3; D011993:Recombinant Fusion Proteins / Q000187:drug effects; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D014326:Tropanes / Q000494:pharmacology; D014982:Xenopus laevis
D036145:Ginsenosides; D018075:RNA, Complementary; D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; D011993:Recombinant Fusion Proteins; D012702:Serotonin Antagonists; D014326:Tropanes; D012701:Serotonin; C026474:ginsenoside Rg2; C042253:bemesetron