Dexamethasone suppresses pituitary-adrenal but not behavioral effects of centrally administered CRF

Intracerebral ventricular (icv) administration of corticotropin-releasing factor (CRF) significantly enhances the expression of stress-related behaviors in the rat and also activates the pituitary-adrenal system. The pituitary-adrenal response can be blocked by pretreatment of animals with dexamethasone. The behavioral effects (motor activation, increased grooming and decreased eating) on the other hand are resistant to suppression by dexamethasone. The independence of the behavioral effects from activation of the pituitary-adrenal axis suggests that stress-induced release of CRF could contribute to behavioral alterations even in the presence of high concentrations of endogenous steroids.