TH and Parkinson disease: Compared with the control group, two out of the 12 studies of MPTP-induced PD showed significant effects of G-Rg1 for improving the rotarod test (P < 0.01), two studies for improving the swim-score values (P < 0.01), six studies for improving the level of TH protein expression (P < 0.01), and two studies for increasing the expression of TH mRNA in the substantia nigra of mice (P < 0.01).