Administration of the neurotoxins 1-Methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) or 6-hydroxydopamine (6-OHDA) also mimics PD symptoms in mice and induces activation and proliferation of microglia, as well as increased expression of inducible nitric oxide synthase (iNOS) and MHC class-I and II molecules [57, 60–64]. Here, NOS2 is linked to Parkinson disease.