Abstract: Objective To investigate the effects and its mechanism of L-theanine on mitochondrial injury induced by the sodium azide in the SH-SY5Y cells. Methods The SH-SY5Y cells were exposed to different concentrations of L-theanine and the sodium azide, the cell viability was measured by the MTT method, the mitochondrial membrane potential was detected by the JC-1 method and the Scanning Confocal Microscopy. The protein levels of intracellular caspase-3, caspase-9 and cytochrome c were detected by the Western Blotting Method. Results (1) With the increase of the concentration of sodium azide, the cell activity decreases gradually. After being pretreated by L-theanine (0.25,0.50,1.00 mmol/L) for 2 hours，it can significantly reduce the cell toxicity and reverse the decline in the mitochondrial membrane potential induced by the sodium azide (0.25 mmol/L) for 24 hours（p<0.05）(2) L-theanine（0.25-1.0 mmol/L）can significantly reverse the increasing of the protein expression level of the caspase-3, caspase-9 and cytochrome c induced by the sodium azide in SH-SY5Y cell（p<0.05）.Conclusion L-Theanine can stabilize mitochondrial membrane potential of the SH-SY5Y cell, reduce the mitochondrial damage.

Key words: mitochondria, sodium azide, theanine, neuroprotective