Rotenone leads to region-specific loss of TH protein and increased density of TH and VGLUT2-colocalizing puncta in the NAc. A, Representative 60× images showing loss of TH signal but no change in VGLUT2 in the CPu of rotenone-treated rats. Scale bar, 20 µm. B, There was a significantly lower TH signal intensity in the CPu (Dunn's post hoc p = 0.048), but not the NAc core (post hoc p > 0.99) or shell (post hoc p > 0.99), after rotenone treatment. Similarly, there was a significantly lower TH puncta density in the CPu (post hoc p = 0.048), but not in the NAc core (post hoc p > 0.99) or shell (post hoc p > 0.99), after rotenone treatment. C, There was no change in the intensity or density of VGLUT2⁺ puncta in nerve terminals within the CPu or NAc of rotenone-treated rats compared with vehicle (Kruskal–Wallis H test, all p > 0.06). D, Representative 60× images of TH (red) and VGLUT2 (green) puncta in the NAc core and shell in vehicle- and rotenone-treated rats. White circles represent colocalizing TH and VGLUT2 puncta. Scale bar, 10 µm. E, Within the NAc, a greater density of TH puncta colocalized with VGLUT2 in the NAc shell compared with the NAc core (Kruskal–Wallis H test, p = 0.031), but there was no significant effect of rotenone (p = 0.061). Data are mean ± SEM. N = 3-6 per group. *p < 0.05 compared with vehicle. ^##p < 0.05 compared with CPu. See Extended Data Figure 6-1.