BZ]To investigate the exact mechanism of melatonin to prohibit the apoptosis of neural cells induced by various kinds of cytotoxic agents. [WT5”BX]Methods. [WT5”BZ]We used the methods of phase contrast microscopy

MTT assay and hoechst dye staining to check this mechanism in SKNSH and U251 cell lines. [WT5”BX]Results. Both 2mmol/L H 2O 2 and 0 5 μ mol/L amyloid β protein （Aβ） induce these two cell lines die via apoptosis. Either melatonin or glutathione can significantly protect both cell lines. The protective effect of 10 μ mol/L melatonin is as same as that of 60 μ mol/L glutathione. [WT5”BX]Conclusion. Melatonin can partly inhibit the cytotoxicity of H 2O 2 and Aβ through its role as a free radical scavenger.