Polygalae radix extract protects cultured rat granule cells against damage induced by NMDA

Polygalae Radix (PR) from Polygala tenuifolia (Polygalaceae) is traditionally used in China and Korea, as this herb has a sedative, anti-inflammatory and antibacterial agent. To extend our understanding of the pharmacological actions of PR in the CNS on the basis of its CNS inhibitory effect, the present study examined whether PR has the neuroprotective action against N-methyl-D-aspartate (NMDA)-induced cell death in primarily cultured rat cerebellar granule neurons. PR, over a concentration range of 0.05 to 5 mug/ml, inhibited NMDA (1 mM)-induced neuronal cell death, which was measured by a trypan blue exclusion test and a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay. PR (0.5 mug/ml) inhibited glutamate release into medium induced by NMDA (1 mM), which was measured by HPLC. Pre-treatment of PR (0.5 mug/ml) inhibited NMDA (1 mM)-induced elevation of intracellular Ca2+ concentration ([Ca2+](i)), which was measured by a fluorescent dye, Fura 2-AM, and generation of reactive oxygen species (ROS). These results suggest that PR prevents NMDA-induced neuronal cell damage in vitro.