Abstract:Objective: To study the neuroprotection of licorice flavonoids on dopamine (DA) neurons and the influence of microglia activation of the substantia nigra compact (SNc) in the mice with Parkinson's disease (PD). Method: The PD mouse models were established by 1,2,3,6-Tetrahydro-1-methyl-4-phenylpyridine;1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP) and the mice were randomly divided into 6 group:control group, model group, levodopa group(40 mg·kg-1), 10,20,30 mg·kg-1 licorice flavonoids group. The drugs were intragastrically perfused to the mice daily for 7 consecutive times.The number of OX-6 immunoreactive cells and DA neurons in the SNc, and the expression level of tyrosine hydroxylase (TH) in ventral midbrain were studied by immunohistochemical analysis and Western blot, and behavior changes were notied after levodopa or licorice flavonoids treatment. Result: Compared with control mice, the PD mice had the typical behaviors of PD, and the number of DA neurons in SNc and the level of TH in ventral midbrain decreased by about 62% and 76%. Meanwhile the number of the OX-6-positive cells in SNc increased markedly(P<0.01). After administered by licorice flavonoids, behavioral symptoms, reduction of DA neurons and increase of OX-6 positive cells in SNc were improved by licorice flavonoids. Especially in 30 mg·kg-1 licorice flavonoids group, those mice with PD had slight behavioral symptoms, and the number of DA neurons in SNc and the expression level of TH in ventral midbrain declined by only about 36% and 42% in compared with the control. Compared with those PD mice without licorice flavonoids, the number of the OX-6 positive cells in the SNc of 30 mg·kg-1 licorice flavonoids group was obviously down-regulated(P<0.01). Compared with those in the levodopa group, the increasing of the number of DA neurons and the decreasing of the number of OX-6 positive cells in 30 mg·kg-1 licorice flavonoids group were significant(P<0.01). Conclusion: These results indicated the neuroprotection effect of licorice flavonoids on DA neurons of SNc in PD mice, and the inhibition of the microglia activation by licorice flavonoids might be responsible for it.
