Ginseng root extract inhibits calcium channels in rat sensory neurons through a similar path, but different receptor, as μ-type opioids

Abstract

The effect of Panax ginseng root extract on Ca 2+ current of adult rat trigeminal ganglion neurons was investigated using whole-cell patch-clamp methods. The application of P. ginseng root extract (100 μg/ml) produced rapid, reversible reduction of the Ca 2+ current by 22 ± 4%. Treatment with pertussis toxin (250 ng/ml) for 16 h reduced the inhibition to 4 ± 1%. The continual presence of 1 μM DAGO, a selective μ-opioid agonist that inhibits Ca 2+ channels, occluded further inhibition of Ca 2+ current by P. ginseng root extract. Yohimbine, phaclofen, atropine, and naloxone — antagonists of α 2-adrenergic, GABA B, muscarinic, and opiate receptors, respectively — did not block the inhibitory effect on Ca 2+ current of P. ginseng root extract. Thus, P. ginseng root extract acts on sensory neurons through a similar pathway as μ-type opioids: both inhibit Ca 2+ channels through pertussis toxin-sensitive GTP-binding proteins. However, the receptor for P. ginseng root extract is not an α 2-adrenergic, GABA B, muscarinic, or opioid receptor.