Following intraventricular, intrastriatal or intranigral delivery, GDNF has reproducibly demonstrated neurorestorative and neuroprotective effects in standard toxin-induced rodent and nonhuman primate models of Parkinson’s disease (PD) (Bjorklund et al. 1997; Gash et al. 1996; Grondin et al. 2002; Tomac et al. 1995; Zhang et al. 1997). This evidence concerns the gene GDNF and Parkinson disease.