GDNF and Parkinson disease: Although glial-derived neurotrophic factor (GDNF) and neurturin (NRTN) are the most studied and promising NTFs in PD, their unintended effects and low clinical benefits direct attention to the other NTFs with a selective trophic activity on DAergic neurons (Bartus and Johnson Jr, 2017[5]; Huddleston and Factor, 2011[12]; Lang et al., 2006[15]).