Mice that started training on the treadmill 1 week before the induction of parkinsonism (METT group) showed a 50% increase in TH-positive neurons in the SNpc and 42% in the VTA, while mice that started training on the treadmill shortly after the induction of parkinsonism (MLTT group) showed 55% increase in the number of dopaminergic neurons in the SNpc and 38% in the VTA compared to sedentary MPTP animals (group M). Here, TH is linked to Parkinson disease.