(a) Adult brain section of BAC-Cck-Cretg/+; R26R-EYFPtg/+ stained with G(Y)FP-specific antibodies (Abs). Cre-mediated EYFP expression is detected in the hypothalamus (HY), cortical layers IV and V (CX) and hippocampus (H). (b) Cellular specificity of Cre-mediated recombination was analysed by double IF using antibodies to YFP and CCK or GABA in the hypothalamus. Quantification was expressed in percentages (n=3, mean±s.d.). (c) Body weight analysis (male mice). Mutants are significantly heavier than controls starting at 4 M of age (1.5 M, n=12 and 13; 3 M, both n=12; 4 M, n=9 and 11; 5 M, n=13 and 17; 7.5 M, n=5 and 7; 11 M, n=6 and 8, for TrkbCck-KO and controls, respectively. Values are mean±s.e.m.). (d) Visible size discrepancy between TrkbCck-KO and control male mice, including fat pad mass. (e) Body composition determined by NMR at 3 M and 9 M. Old but not young TrkbCck-KO mice show increased FM but no changes in FFM (9 M, FM, TrkbCck-KO, 12.37±0.96 g (n=5) versus 5.54±0.86 (n=6), P=0.0005, unpaired Student’s t-test; FFM, TrkbCck-KO, 31.37±0.87 g (n=5) versus 29.08±1.33 (n=6); 3 M, FM, TrkbCck-KO, 4.16±0.86 g (n=4) versus 2.18±0.19 (n=4), P=0.06, unpaired Student’s t-test; FFM, TrkbCck-KO, 24.74±0.96 g (n=4) versus 23.84±0.42 (n=4); mean±s.e.m. (f) Light and dark phases average food intake (2 M, n=4 for all); (8 M, n=6 for all), mean±s.e.m. (g) Similar cumulative food intake observed over 3 weeks for 3 M TrkbCck-KO and controls (n=6 for all; mean±s.e.m.). (h) Average daily food intake over 6 days on SC and HFD (third week is shown) (two-way ANOVA, diet effect: F(1,8)=24.9, P=0.001, Fisher’s PLSD P=0.001; genotype effect, diet*genotype effect were not significant). This experiment was replicated on two independent mouse cohorts. Scale bars, (a) 500 μm; (b) 50 μm.