Central Effects of Ginsenosides on the Feeding Behavior and Response to Stress in Rats

To clarify central mechanisms of ginsenosides, changes in ingestive and ambulatory behaviors were investigated in rats after single or continuous infusion into the third cerebroventricle or various hypothalamic loci. Following single infusion into the third cerebroventricle, ginsenoside Rbl at doses of 0.05, 0.10 and 0.20 $\mu$mol dose-dependently decreased food intake. None of the doses tested affected ambulation. Drinking suppression was only observed at the maximum dose of 0.20 $\mu$mol. Equimolar injections into the peritoneum had no effects on ingestive behavior or ambulation. These findings indicated that ginsenoside Rbl specifically and centrally inhibited food intake. According to analyses of daily feeding patterns, this feeding suppression was the result of a decrease in meal size, not from changes in the postprandial intermeal interval or eating speed. The suppressed food intake was accompanied by hyperglycemia, leaving plasma insulin unaffected. Unilateral micro injection of 0.01 u mot ginsenoside Rb, into the ventromedial hypothalamus specifically decreased food intake, although equimolar injection into the lateral hypothalamic area did not affect food intake. Following continuous infusion of Rg, into the third cerebroventricle, the feeding inhibition due to surgical operation was attenuated. Rbs administered by the same procedure abolished the toxic effect of toxohormone-L on food intake. Taken together, these findings suggest that ginsenoside as a whole may have pharmacological potency to maintain feeding at a certain physiological level.