BDNF and Parkinson disease: The authors intraperitoneally administered 1-methyl-phenyl-1,2,3,6-tetrahydropyridine (MPTP neurotoxin) alone and along with a TrkB antagonist—K252a—which resulted in clear PD-like outcomes using behavioral (balance beam test and pole test) and histological (the number of TH-positive neurons and apoptotic cells in the substantia nigra) criteria, but not with biochemical markers (BDNF and TrkB).