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

The effect of Panax ginseng root extract on Ca2+ current of adult rat trigeminal ganglion neurons was investigated using whole-cell patch-clamp methods. The application of P. ginseng root extract (100 micrograms/ml) produced rapid, reversible reduction of the Ca2+ 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 microM DAGO, a selective mu-opioid agonist that inhibits Ca2+ channels, occluded further inhibition of Ca2+ current by P. ginseng root extract. Yohimbine, phaclofen, atropine, and naloxone--antagonists of alpha 2-adrenergic, GABAB, muscarinic, and opiate receptors, respectively--did not block the inhibitory effect on Ca2+ current of P. ginseng root extract. Thus, P. ginseng root extract acts on sensory neurons through a similar pathway as mu-type opioids: both inhibit Ca2+ channels through pertussis toxin-sensitive GTP-binding proteins. However, the receptor for P. ginseng root extract is not an alpha 2-adrenergic, GABAB, muscarinic, or opioid receptor.