NOS2 and Parkinson disease: nNOS and iNOS are acknowledged to be closely related to the pathogenesis of PD, for example, nNOS inhibitor has a dose-dependent protective effect against 1-methyl-4- phenyl-1,2,3,6- tetrahydropyridine (MPTP)-induced striatal dopamine and 3,4- dihydroxyphenylacetic acid depletion in mice, and dopaminergic neurons in the SNPc of iNOS-deficient mice were almost completely protected from MPTP toxicity in a chronic paradigm of MPTP toxicity [45], [46].