Tyrosine hydroxylase expression and activity in nigrostriatal dopaminergic neurons of MPTP-treated mice at the presymptomatic and symptomatic stages of parkinsonism.

Progressive degeneration of nigrostriatal dopaminergic (DA-ergic) neurons is a key component in the pathogenesis of Parkinson's disease, which develops for a long time at the preclinical stage with no motor dysfunctions due to the initiation of compensatory processes. The goal of this study was to evaluate the changes in surviving nigrostriatal DA-ergic neurons with focus on tyrosine hydroxylase (TH) in MPTP-treated mice at the presymptomatic and early symptomatic stages of parkinsonism. According to our data, a partial degeneration of DA-ergic neurons at the presymptomatic stage was accompanied by: (i) no change in TH mRNA content in the substantia nigra (SN) suggesting a compensatory increase of TH gene expression in individual neurons; (ii) a decrease of TH protein content in the nigrostriatal system and no change in individual neurons, suggesting a slowdown of TH translation.