At the conclusion of experiments, NCD- and HFD-fed C57BL/6 mice were perfused with a 4% paraformaldehyde solution. Whole brains were removed, then stored in 4% paraformaldehyde for 3 days. After transferring brains to a 30% sucrose solution, coronal sections (25 µm thick) were prepared, washed with PBS, and then blocked by incubating for 1 hour with 3% donkey serum (Dako, Glostrup, Denmark) and 0.3% Triton X-100 in the dark. Thereafter, sections were washed with PBS and incubated overnight at 4℃ with anti-TH (1:500; Millipore, MA, USA) and anti-pJNK (1:500; Invitrogen, Carlsbad, CA, USA) antibodies, diluted in blocking solution. Sections were then washed with PBS and incubated with fluorescently labeled secondary antibody for 1 hour at room temperature. Sections from SN was obtained through -2.60 mm to -3.90 mm relative to bregma [39 (link)]. Sections from striatum was obtained through -1.08 mm to -0.84 mm relative to bregma [40 (link)]. TH and pJNK fluorescence (n=10 slides per condition, n=6 each groups) were visualized using an IX70 confocal microscope (Olympus, Tokyo, Japan).