Rotenone-induced nigrostriatal degeneration causes motor deficits in adult rats. A, Representative images of Nissl-stained midbrain from rotenone- or vehicle-treated rats, indicating substantial neuronal cell body loss in the SNc in response to rotenone; 20× magnification. Dashed lines indicate SNc. Scale bar, 100 µm. B, Representative images of TH-immunostained DA neurons (red) from the SNc (left) and striatum (right) from vehicle- or rotenone-treated rats; 20× magnification. Dashed lines indicate SNc. Scale bars, 100 µm. C, Quantification of immunostained TH⁺ DA neurons in the SNc (Mann–Whitney U test, p = 0.0025) and (D) TH fluorescence intensity from TH⁺ nerve terminals in the dorsolateral striatum showed significant loss in response to rotenone compared with vehicle (Mann–Whitney U test, p = 0.0022). Striatal TH fluorescence intensity is normalized to vehicle condition. E, PIT of vehicle (black)- or rotenone (red)- treated rats shows impairment in rotenone-treated rats (H₁₄ = 41.8, p < 0.001). Data are mean ± SEM. N = 5-7 per group for stereology and immunohistochemistry. N = 3 per group for PIT. *p < 0.05. **p < 0.01.