Administration of neurotrophic factors such as brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) are generally recognized as powerful survival factors for the degenerated dopaminergic neurons and the nigro-triatal pathway in PD (Cass et al., 2006; Kramer and Liss, 2015; Sun et al., 2015). Here, GDNF is linked to Parkinson disease.