Neuroprotective Effects of Methanol Extract of Sophorae Subprostratae Radix on Glutamate Excitotoxicity in PC12 Cells and Organotypic Hippocampal Slice Cultures

Objectives : It has been reported that Sophorae Subprostratae Radix (SSR) has a neuroprotective effect on cerebral ischemia in animals. In the present study, the authors investigated the neuroprotective effect of SSR on glutamate excitotoxicity. Glutamate excitotoxicity was induced by using NMDA, AMPA, and KA in PC12 cells and in organotypic hippocampal slice cultures. Methods :Methanolic extract of SSR was added at 0.5, 5, and 50 ${\mu}$g/ml to culture media for 24 hours. The effects of SSR were evaluated by measuring of cell viability, PI-stained neuronal cell death, TUNEL-positive cells, and MAP-2 immunoreactivity. Results : SSR increased PC12 cell viabilities significantly against AMPA-induced excitotoxicity, but not against NMDA-induced or KA-induced excitotoxicity. In organotypic hippocampal slice cultures damaged by NMDA-induced excitotoxicity, SSR attenuated neuronal cell death significantly in the CA1, CA3, and DG hippocampal regions and reduced TUNEL-positive cells significantly in CA1 and DG regions. In organotypic hippocampal slice cultures damaged by AMPA-induced excitotoxicity, SSR attenuated neuronal cell death and reduced TUNEL-positive cell numbers significantly in the CA1 and DG regions. In organotypic hippocampal slice cultures damaged by KA-induced excitotoxicity, SSR attenuated neuronal cell death significantly in CA3, but did not reduce TUNEL-positive cell numbers in CA1, CA3 or DG. In organotypic hippocampal slice cultures damaged by NMDA-induced excitotoxicity, SSR attenuated pyramidal neuron neurite retraction and degeneration in CA1. Conclusions : These results suggest that the neuroprotective effects of SSR are related to antagonistic effects on the NMDA and AMPA receptors of neuronal cells damaged by excitotoxicity and ischemia.