A–H, GDNF+/− mice treated with METH exhibited an inflammatory response in the SN 2 weeks after injection. CD45-IR in the SN (A–D) and striatum (E–H) in saline (SAL)-treated WT mice (A, E), saline-treated GDNF+/− mice (B, F), METH-treated WT mice (C, G), and METH-treated GDNF+/− mice (D, H). Scale bar, 0.5 mm. I, J, Quantitation of the average integrated density of CD45-ir in the SN (I) and striatum (J). Saline-treated GDNF+/− mice had more CD45-IR in the SN than saline-treated WT mice (*p < 0.05). METH treatment caused a significantly greater increase in CD45-IR in the SN of GDNF+/− mice than in saline-treated GDNF+/− mice or METH-treated WT mice (*p < 0.05). n = 5 per group. Error bars indicate SEM.