Histopathological alterations can be seen after IP MPTP injection, but not oral application.

(A) Representative pictures of the striatum after anti-tyrosine hydroxylase (TH) staining and quantification (B). Mice were investigated two days after MPTP treatment. Reduction of TH positive fibers is only seen in IP treated animals (p<0.001). Animals were either treated four times (4×) with 15 mg/kg MPTP (see Methods) or with one (1×) single dose of 60 mg/kg. Scale bars: 50 µm. n = 3, striatal fibers were analyzed in a field of 45×45 µm. Error bars represent SEM.