The expression of TH was decreased in aged control group (0.73±0.08) and aged LPS-PD group (0.46±0.07) as compared with young control group (1.16±0.07,p<0.001) and young LPS-PD group (0.68±0.04, p<0.05), which indicated that there had the relationship between the loss of DA neurons and aging (Fig. 1D). Here, TH is linked to Parkinson disease.