Rodents (Table 2, a) and non-human primates (Table 2, b) with a unilateral or bilateral lesion of the nigrostriatal pathway using specific neurotoxins to model PD have been used to show the preventive and restorative effects of GDNF on DA neuron survival, levels of dopamine, and its catabolites, and motor deficits (see reviews [125,126,127,128,129,130]). This evidence concerns the gene GDNF and Parkinson disease.