(a–e) Images show hypothalamic in situ hybridization for several markers of PVN neuronal activity in 5-month-old animals. Crh and Avp expression highlight the PVN. Penk is expressed at very low levels in the PVN and higher levels in an adjacent nucleus. (a,b) Staining density for Crh (TrkbCck-KO, 1.108±0.043 versus control, 1.00±0.023, P=0.04, unpaired Student’s t-test, values are mean±s.e.m., n=7 per genotype). (c,d) Avp (staining density: TrkbCck-KO, 0.805±0.043 versus control 1.00±0.050, P=0.02, unpaired Student’s t-test, values are mean±s.e.m., n=6 per genotype). (e,f) Penk TrkbCck-KO (integrated density: TrkbCck-KO, 1.717±0.243 versus control 1.000±0.204, P=0.009, unpaired Student’s t-test, values are mean±s.d., n=3 per genotype). (g) Fold difference of gene expression in PVN tissue punches between control and TrkbCck-KO mutants (n=4 per genotype), unpaired Student’s t-test, values are mean±s.e.m. Scale bars in a, c and e, 100 μm. Avp, arginine vasopressin; Penk, proenkephalin.