ACHE and Parkinson disease: In the present study, we investigated the neuroprotective effects of quercetin to modify glutathione peroxidase (GPx), superoxide dismutase (SOD), Na+, K+-ATPase, immunoreactivity of 4-hydroxy-2-nonenal (4-HNE), acetylcholinesterase (AChE) activities, and the level of dopamine (DA) in the brain tissue in the MPTP-induced mouse model of Parkinson's disease.