TH and Parkinson disease: To assess changes in dopaminergic projections in the nigrostriatal pathway in a mouse model of Parkinsonism, immunohistochemical staining against tyrosine hydroxylase (or tyrosine 3-monooxygenase; EC 1.14.16.2; TH) and a computer-assisted densitometric analysis of TH-ir neurons in the SNpc and the target dopaminergic projection in the striatum were performed.