CRF is required for the phasic firing induced increase in BDNF in NAc in the context of stress. (a) Timeline of animals that received intra-NAc CRF antagonist infusions. (b) Intra-NAc CRF antagonist (alpha-helical CRF) infusion eliminates social avoidance seen with subthreshold stress plus phasic stimulation of VTA-NAc neurons (F2,21=3.99, *P<0.05, n=6–9) and (c) blocks the expected BDNF increase in NAc (F2,18=4.66, *P<0.05, n=6–8). (d) Timeline of stress-naïve animals that received intra-NAc CRF infusions. (e) Intra-NAc CRF infusions in stress-naïve animals does not alter social interaction behavior (F2,23=0.58, P=0.57, n=8–9). (f) Phasic stimulation alone induces an increase in NAc BDNF levels in intra-NAc CRF infused, stress-naïve mice (F2,19=5.88, *P<0.01, n=6–8). (g) Timeline of stress and stimulation-naïve animals that received intra-NAc CRF infusions. (h) Intra-NAc CRF infusions in stress and stimulation-naïve animals does not alter social interaction behavior (F5,12=0.082, P=0.922, n=5). (i) Intra-NAc CRF infusions of 1 or 5 μg does not alter NAc BDNF levels (F2,12=0.186, P=0.833, n=5).