Paeonolum restored the MPP+-induced decrease in the total level of GSH in PC12 cells. Cells were preincubated with paeonolum for 30 min and then exposed to 250 μM MPP+ for further 24 h. Pretreatment with different concentrations of paeonolum significantly attenuated MPP+-induced decrease in total GSH level at 24 h following MPP+. The total level of GSH (reduced form GSH + oxidized form GSSG) was determined using glutathione reductase. Quantitative data are presented in the bar graph. Values are means ± SEM. *P < 0.01 compared with vehicle control. The results were obtained from three independent experiments performed in triplicate.