Effects of ginseng saponins on responses induced by various receptor stimuli

Abstract We investigated the effects of four ginseng saponins, ginsenoside-Rb 1 , -Rg 2 , -Rg 3 and -Ro, on the responses induced by receptor stimulation of various stimuli. Ginsenoside-Rg 2 (1–100 μM) reduced the secretions of catecholamines from bovine adrenal chromaffin cells stimulated by acetylcholine and γ-aminobutyric acid but not by angiotensin II, bradykinin, histamine and neurotensin. In guinea-pig, the ginsenoside also diminished the nicotine-induced secretion of catecholamines from the adrenal chromaffin cells, but it did not affect the muscarine- and the histamine-induced ileum contractions. On the other hand, ginsenoside-Rg 3 (1–100 μM) reduced not only the acetylcholine-, the γ-aminobutyric acid- and the neurotensin-induced secretions but also, at a higher concentration (100 μM), the angiotensin II-, the bradykinin- and the histamine-induced secretions from the bovine chromaffin cells. Furthermore, the saponin (3–100 μM) significantly inhibited the muscarine- and the histamine-induced ileum contractions of the guinea-pig. Ginsenoside-Rb 1 and -Ro had no marked effect on their responses. These results strongly suggest that ginsenoside-Rg 2 is a potent selective blocker of nicotinic acetylcholine and γ-aminobutyric acid receptors (ionotropic receptors) and ginsenoside-Rg 3 is not only a blocker of ionotropic receptors but also an antagonist of muscarinic or histamine receptors.