Paeonolum inhibited MPP+-induced the release of cytochrome c. PC12 cells were treated with 250 μM MPP+ for 24 h in the presence or absence of paeonolum (50, 100, 150 μM). Cytochrome c release was determined by Western blot analysis. The amount of cytochrome c was estimated by densitometric analysis of each protein band. The data are represented as means ± SEM for three independent experiments. *P < 0.01 vs. group treated with MPP+ alone.