Objective:To investigate dopaminergic neuron injury and α-synuclein expression of mouse exposed chronically to low dose of 1-methyl-4-phenyl-1

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6-tetrahydropyridine(MPTP). Methods:The C57BLmice received bake hypodermic injections of 25 mg/kg MPTP twice a week for 5 consecutive weeks. Abnormal behavior was observed during the treatment by using herbicide. The expression of throsine hydroxylase(TH)and α-synuclein was determined by immunohistochemistry. The dopaminergic neurons apoptosis was determined by TdT-mediatd dUTP-biotin nick end labeling (TUNEL). Results:As compared with the controls of mice

those treated with MPTP displayed markedly hypoactive behavior. Immunohistochemical staining showed that the numbers of TH stain cells was decreased significantly after treatment with MPTP

and the density of α-synuclein stain was increased significantly after treatment with MPTP. Apoptosis displayed after treatment with MPTP. Conclusion:Chronical injection with MPTP might induce abnormal behavior. apoptosis and continual aggregation of α-synuclein in dopaminergic neurons of substantial nigra.