CRF receptor type 1 and 2 expression and anatomical distribution in the rat colon

Corticotropin-releasing factor (CRF) receptor agonists administered peripherally increase colonic propulsive motility and fecal output in experimental animals. In addition, endogenous CRF-related peptides are found in the lower gastrointestinal (GI) tissues, suggesting a local expression of CRF receptors. In the present study, we report the expression of both CRF receptor type 1 (CRF1) and 2 (CRF2) in the rat colon at the mRNA and protein levels. For the purpose of receptor protein mapping, a specific antiserum against the C-terminus of CRF2 (2064a-CRF2) was generated and characterized. This antiserum in conjunction with a selective anti-CRF1 antiserum (4467a-CRF1) was used in immunofluorescent staining to demonstrate the anatomical distribution of receptor protein expression. Using RT-PCR for the CRF1 and CRF2 genes, both receptor gene transcripts were found in RNA isolated from crude colonic samples. CRF1 was found in the goblet and stem cells of the colonic crypts and in scattered cells of the surface epithelium and the lamina propria of the proximal colonic mucosa. In addition, double staining against neuron-specific antigens revealed CRF1 expression in the myenteric and submucosal nervous plexus. CRF2 expression was localized mainly in the luminal surface of the crypts and in blood vessels of the submucosal layer. These results demonstrate expression of both CRF receptor types in the rat colon and support a role for their involvement in regulating peripheral effects of CRF ligands.