Effect of ginseng saponins on β-amyloid-suppressed acetylcholine release from rat hippocampal slices

In view of the facts that ginseng has been shown to improve age-related memory deficits and beta -amyloid-related peptides have been suggested to play a significant role in memory degeneration in the elderly, the present study was carried out to examine the effect of various ginsenosides on beta -amyloid peptides-modulated acetylcholine (ACh) release, a key neurotransmitter in memory processing, from the hippocampal slices. Addition of beta -amyloid fragment(25-35) (0.01-1 muM) in the superfusion medium suppressed the K+-evoked [H-3]-ACh release from the rat hippocampal slices in a concentration-related manner and about 40% reduction in ACh outflow was observed when incubating with the highest concentration of an amyloid fragment (1 muM). Inclusion of the ginsenoside components Rb-1 (0.1 muM), but not Rg(1), caused a rightward shift of the concentration-response curve of beta -amyloid. The reversal of the beta -amyloid-inhibited ACh release by Rb-1 was not blocked by tetrodotoxin (1 muM) indicating that an interaction occurs at the cholinergic synapse. These results suggest that Rb-1 may elicit its anti-amnesic effect by minimizing the inhibitory effect of beta -amyloid peptides.