Catalpol, a component of shú dì huáng, is used in mice with PD and it is found that it can exert a protective effect on DA neurons and improve the behavioral scores of Parkinson’s mice, by up-regulating the content of DA and its major metabolites (DOPAC and HVA) in the striatum and by increasing the number of Tyrosine hydroxylase positive cells and the content of glial cell-derived neurotrophic factor (Xu et al., 2010). Here, TH is linked to Parkinsonism.