BLOCKADE OF THE HYPOTHALAMIC-PITUITARY-ADRENAL RESPONSE TO STRESS BY INTRAVENTRICULAR-INJECTION OF DEXAMETHASONE - A METHOD FOR STUDYING THE STRESS-INDUCED PERIPHERAL EFFECTS OF GLUCOCORTICOIDS

Interest in the mechanisms whereby stressors can influence behavior an d physiological functioning has involved the use of a variety of metho ds to prevent the stress-induced release of glucocorticoids, an import ant and commonly studied stress hormone. We examined the effect of int racerebral ventricular dexamethasone (ICV DEX) on the stress-induced r elease of adrenocorticotropic hormone (ACTH). corticosterone, plasma e pinephrine (E), and plasma norepinephrine (NE). Male Sprague-Dawley ra ts were stereotaxically implanted with third ventricle ICV cannulae, a dministered DEX or vehicle, and exposed to 100 1.6-mA tail shocks. Str ess hormones were assessed from blood taken during and after the cessa tion the shock. We report an ICV DEX injection protocol (10 mug given four times) that results in blocking the stress-induced release of ACT H and corticosterone, and attenuating the stress-induced release of pl asma E and NE. We hypothesize that ICV DEX reduces hypothalamic cortic otropin releasing hormone (CRH) synthesis and/or release. This method would be especially useful for those studying the effect of pituitary- adrenal hormones on steroid sensitive peripheral targets, such as the immune system.