TH and Parkinson disease: Compared with the control group, the count of immunopositive cells and protein expression of SNc TH, and the content of immunopositive fiber terminals in the striatal TH of the PD group declined, with statistically significant differences (P < 0.01); compared with the PD group, the count of immunopositive cells and protein expression of SNc TH, and the content of immunopositive fiber terminals in the striatal TH of the PD + exercise group had no significant change, with no statistically significant difference (P > 0.05, Figure 7).