[Effects of ginseng saponins on receptor stimulation-responses]

We investigated the effects of root of Panax ginseng C. A. Meyer on the secretion of catecholamines (CAs) from bovine adrenal chromaffin cells stimulated by acetylcholine (ACh). In two major parts, nonsaponin and crude saponin fractions from the root, the crude saponin but not the non-saponin greatly reduced the ACh-evoked secretion. Furthermore, various purified ginseng saponins (ginsenosides) had a tendency to reduce the secretion. Most effective saponin was ginsenoside (G) RG2. GRg2 also inhibited the ACh-evoked Na+ and Ca2+ influxes into the cells. The GRg2 inhibition of the secretion was overcome by increasing the external Na+ but not Ca2+ concentrations. However, GRg2 did not affect the secretion from the cells induced by high K+, which is regarded as directly depolarizing the cell membranes and causing Ca2+ influx through voltage-sensitive Ca2+ channels. Therefore, the root of Panax ginseng contains ingredients, that is saponins, which inhibit the secretion of catecholamines from the cells stimulated by ACh. The inhibition is probably due to the antagonism of nicotinic acetylcholine receptor-operated cation channels. GRg2 had no effects on other receptor stimulation-responses but GRg3 inhibited them. These may be why the root of Panax gingseng has a variety of pharmacological effects.