Changes of [³H]MK-801, [³H]muscimol and [³H]flunitrazepam binding in rat brain by the prolonged ventricular infusion of ginsenoside Rc and Rg1

In the present study, we have investigated the effects of centrally administered ginsenoside Rc and Rg1 on the modulation of the NMDA receptor and GABA_A receptor binding in rat brain. The NMDA receptor binding was analysed by quantitative autoradiography using [³H]MK-801 binding, and the GABA_A receptor bindings were analysed by using [³H]muscimol and [³H]flunitrazepam binding in rat brain slices. Rats were infused with ginsenoside Rc or Rg1 (10 μg/10 μl h^-1, i.c.v.) for 7 days, through pre-implanted cannula using osmotic minipumps (Alzet, model 2ML). The levels of [³H]MK-801 binding were highly decreased in part of the parietal layers of the cortex and cingulated by ginsenoside Rc and Rg1. The levels of [³H]muscimol binding were strongly elevated in almost all regions of the frontal cortex by the treatment of ginsenoside Rc but decreased by ginsenoside Rg1. However, the [³H]flunitrazepam binding was not modulated by ginsenoside Rc or Rg1 infusion. These results suggest that prolonged infusion of ginsenosides could differentially modulate [³H]MK-801 and [³H]muscimol binding in a region-specific manner.