GINSENG ROOT PREVENTS LEARNING-DISABILITY AND NEURONAL LOSS IN GERBILS WITH 5-MINUTE FOREBRAIN ISCHEMIA

The present study was designed to investigate the possible neuroprotec tive activity of ginseng roots in 5-min ischemic gerbils using a step- down passive avoidance task and subsequent neuron and synapse counts i n the hippocampal CA1 region. The following drugs were administered fo r 7 days before the induced ischemia: red ginseng powder (RGP), crude ginseng saponin (CGS), crude ginseng non-saponin (CGNS), and pure gins enosides Rb-1, Rg(1) and Ro. Oral administration of RGP significantly prevented the ischemia-induced decrease in response latency, as determ ined by the passive avoidance test, and rescued a significant number o f ischemic hippocampal CA1 pyramidal neurons in a dose-dependent manne r. Intraperitoneal injections of CGS exhibited a similar neuroprotecti ve effect. CGNS had a significant but less potent protective effect ag ainst impaired passive avoidance task and degeneration of hippocampal CAI neurons. Ginsenoside Rb-1 significantly prolonged the response lat ency of ischemic gerbils and rescued a significant number of ischemic CA1 pyramidal neurons, whereas ginisenosides Rg(1) and Ro were ineffec tive. Postischemic treatment with RGP, CGS or ginsenoside Rb-1 was ine ffective. The neuroprotective activities of RGP, CGS and ginsenoside R b-1 were confirmed by electron microscopy counts of synapses in indivi dual strata of the CA1 field of ischemic gerbils pretreated with the d rugs. These findings suggest that RGP and CGS are effective in the pre vention of delayed neuronal death, and that ginsenoside Rb-1 is one of the neuroprotective molecules within ginseng root.