BDNF and Parkinson disease: Diminished amounts of brain-derived neurotrophic factor (BDNF) have been found in cerebrospinal fluid (CSF) within the ventricular or lumbar regions, autopsy reports of PD patient brains, and in Parkinson disease-induced [1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA)] animal models (Nagatsu and Sawada, 2005).