Mice (C57Bl/6) were pretreated with the indicated dose of 10 nm CeONP in saline-citrate, followed by MPTP challenge 5 days later (6 animals per group). Animals were euthanized 7 days after MPTP administration, brains were perfusion fixed, and stained for tyrosine hydroxylase (TH+, brown), a marker of dopaminergic neurons. Nuclei are counterstained with Nissl (blue). Note the almost complete destruction of dopaminergic neurons by MPTP (upper rt panel), which was abrogated in CeONP-treated mice (lower 2 panels).