The major pathological change at this stage was 44% loss of TH+ axonal terminals in the dorsal striatum (TH+ terminal optical density: 1823 ± 186 in 12 control vs. 1023 ± 89 in six MitoPark mice, averaged from eight sequential brain sections from Bregma 1.20 mm to −0.03 mm, Fig. 4c, d, f, Supplementary Fig. 5), making them an ideal model for studying the ultra-early stage of PD. Here, TH is linked to Parkinson disease.