BDNF is necessary for the optogenetically induced susceptible phenotype. (a) Schematic and timeline of VTA-NAc neurons with cannula implantation into NAc for infusion of the TrkB inhibitor, ANA-12, 1 hr prior to behavior test with optical stimulation. (b) Intra-NAc ANA-12 infusions eliminates social avoidance with phasic stimulation (F2,23=5.59, **P<0.01, n=6–10), but (c) does not prevent the increase in BDNF levels in NAc (F2,22=16.18, **P<0.01, n=8–9). (d) Schematic and timeline showing targeting of VTA-NAc cells in fl/fl BDNF and control animals. (e) Phasic stimulation of VTA-NAc cells does not induce social avoidance in fl/fl BDNF mice (unpaired t-test, t11=2.9, P<0.01; n=6–7) and (f) does not increase BDNF in NAc (unpaired t-test, t9=4.78, **P<0.01; n=5–6).