Role of corticotropin-releasing factor receptors type 1 and 2 in modulating the rat adrenocorticotropin response to stressors

Abstract

We investigated the contribution of corticotropin-releasing factor (CRF) receptors types 1 and 2 (CRF1 and CRF2) in mediating the ACTH response to shock, alcohol injection, or endotoxemia in the rat. Peptidic (Astressin B and Astressin2-B) and nonpeptidic (NBI30775) CRF antagonists were injected iv before the stressors at doses previously shown to be effective in blocking the corresponding receptors. Because NBI 30775, which specifically blocks CRF1, penetrates the brain following systemic injection, we also compared its effect with that of Astressin B, which primarily, though not exclusively, targets CRF1 but does not cross the blood-brain barrier. Shocks, alcohol (4.5 g/kg, intragastrically) or lipopolysaccharide (LPS, 1 μg/kg, iv) all significantly released ACTH. Astressin B or NBI 30775 markedly decreased the effect of shocks or alcohol and also interfered, though less significantly so, with the influence of LPS. In contrast, specific blockade of CRF2 with Astressin2-B, although not significantly altering the overall ACTH response to shocks, alcohol, or LPS, slightly enhanced ACTH levels during the early phase of some of these responses. Interestingly, combined administration of NBI 30775 and Astressin2-B decreased ACTH levels more than NBI 30775 alone, although this difference did not reach statistical significance. Finally, blockade of CRF1 and/or CRF2 augmented LPS- induced TNF-α and IL-6 release. Collectively, there results confirm the critical role played by CRF1 in mediating the ACTH response to shocks, alcohol and LPS, whereas the influence of CRF2 remains subtle. Finally, we showed that peripheral endogenous CRF restrains the ability of LPS to release cytokines.