BDNF and depressive disorder: Considering the role of BDNF–TrkB signaling in the NAc in depression,16, 30, 33, 44, 45, 46 our findings suggest that a marked increase of BDNF within the NAc by repeated METH exposure contributes to long-lasting behavioral abnormalities (depression and behavioral sensitization) and that TrkB antagonists confer beneficial effects against these behavioral abnormalities by blocking TrkB signaling in the NAc shell, but not NAc core.