Comparison of central administration of corticotropin-releasing hormone and urocortin on food intake, conditioned taste aversion, and c-Fos expression

Corticotropin-releasing hormone (CRH) is a potent regulator of the hypothal amic-pituitary-adrenal axis, and reduces food intake when administered into the third cerebral ventricle (i3vt). However, CRH also promotes conditione d taste aversion (CTA) learning which indicates that its anorectic effects are accompanied by aversive consequences that would reduce food intake inde pendently of energy regulation. Urocortin (Ucn) is a closely related mammal ian peptide that binds to both identified CRH receptor subtypes and also re duces food intake when administered i3vt. The present experiments compared the aversive consequences of i3vt administration of CRH and Ucn at doses th at produced comparable decrements in food intake. Experiment 1 found that 1 .0 mu g Ucn and 2.0 mu g CRH produced similar reductions in food intake. Ex periment 2 demonstrated that, at these doses, CRH but not Ucn promoted robu st and reliable CTA learning. A third experiment showed comparable increase d c-Fos-like immunoreactivity after Ucn and CRH in forebrain and hindbrain structures associated with food intake. It is concluded that Ucn, at doses that reduce food intake to levels like that observed after administration o f CRH, do not produce similarly aversive consequences. (C) 2000 Elsevier Sc ience Inc. All rights reserved.