Serotonergic function is altered in the raphe nuclei of CRFR2-null mice. (A-E) LCMRglu in the dorsal raphe nucleus (DRN) and median raphe nucleus (MRN) is lower in CRFR2-null mice than controls under basal conditions. (A,C) 8-OH-DPAT or (B,D) DOI administration decreased LCMRglu in the (A,B) DRN or (C,D) MRN only in control mice. (E) Colour-coded autoradiograms from coronal brain sections at the level of the midbrain raphe. ‘Warm’ colours represent high levels of [14C]-2-deoxyglucose accumulation while ‘cold’ colours represent low tracer accumulation. Images were selected from animals with matched plasma tracer and glucose concentrations. 5-HIAA and 5-HT content of the (F) dorsal and (G) caudal subdivisions of the DRN showed that the 5-HIAA:5-HT ratio was higher in CRFR2-null mice under basal conditions in the dorsal DRN (DRD) and was lowered by ARS only in CRFR2-null mice in both DRD and caudal DRN (DRC). Data expressed as mean ± SEM. N = 8 for LCMRglu, ANOVA critical F(1,28) value = 4.196 for P ≤ 0.05, 7.636 for P ≤ 0.01, 13.500 for P ≤ 0.001. N = 6 or 7 for 5-HIAA and 5-HT content, ANOVA critical F(1,22) values = 4.301 for P ≤ 0.05, 7.945 for P ≤ 0.01, 14.380 for P ≤ 0.001. *P < 0.05, **P < 0.01 in post-hoc analysis.