TH and Parkinson disease: The fluorescent images of TH positive (TH+) neurons in SNpc and TH+ fibers in the striatum are shown in Fig. 9A and B, respectively, with semi-quantitative data summarized in Fig. 9D and E. Compared with the saline group after 14 days, the hydrogel-treated PD rats showed significant increases in the number and fluorescence intensity of TH+ neurons in the SNpc, especially for COA2 and curcumin-loaded COA2 groups.