GDNF and Parkinson disease: The study performed by Lau et al. [26] has revealed that the neuronal and behavioral recovery produced by exercise in the chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD was associated with an improved mitochondrial function and an increase in the brain region-specific levels of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF).