Effects of the ginsenosides Rg1 and Rb1 on morphine-induced hyperactivity and reinforcement in mice

Recent studies have demonstrated that ginseng saponin inhibits the hyperactivity and conditioned place-preference response induced by psychostimulants and opiates. This seems to occur by direct or indirect modulation of dopaminergic activity. However, it is not known which components of ginseng saponin are active. These experiments were conducted to determine the effects of the ginsenosides Rb-1 and Rg(1), major components of the protopanaxadiol and protopanaxatriol fractions of ginseng saponin, on morphineinduced hyperactivity and conditioned place-preference. Morphine-induced hyperactivity, but not apomorphine-induced climbing behaviour, was inhibited by both Rb-1 and Rg(1). These findings confirm the hypothesis that ginsenosides modulate catecholaminergic activity preferentially at pre-synaptic sites. Morphine-induced conditioned place-preference was inhibited by Rg(1), but not by Rb-1. It has previously been shown that at low doses Rb-1 and Rg(1) are equally effective at inhibition of catecholamine secretion at the pre-synaptic site, but that at high doses Rg(1) is a more effective inhibitor. This observation might explain our finding that morphine-induced conditioned place-preference was inhibited by Rg(1) only. Our findings suggest that Rg(1), a component of ginseng saponin with appropriate activity, might be a useful agent for prevention and treatment of the adverse effects of morphine.