TH and Parkinson disease: This MPTP intoxication regimen reproducibly induced the loss of around 50% of the dopaminergic neurons of the substantia nigra pars compacta (SNpc) as evidenced on tyrosine hydroxylase–immunostained (TH-immunostained) brain sections and by the stereological quantification of TH+ neurons of the whole SNpc (Figure 1, A and B), mimicking the pathognomic change underlying PD (27–30).