Activity in the hypothalamo-hypophyseal-adrenocortical system on experimental induction of chronic fatigue syndrome.

Changes in the activity of the hypothalamo-hypophyseal-adrenocortical system (HHACS) were studied in an experimental model of chronic fatigue syndrome induced by i.p. administration of synthetic doublestranded RNA (polyriboinosinic:polyribocytidylic acid, Poly I:C) at a dose of 3 mg/kg. Functional changes in the different components of the HHACS were detected using standard tests with i.p. ACTH or hydrocortisone on the background of cold stress and injections of Poly I:C. Single doses of Poly I:C were followed by the development of impairments to HHACS function, with decreases in the ACTH sensitivity of adrenal cells and suppression of the negative feedback mechanism, resulting in significant decreases in corticosterone concentrations in standard tests with administration of ACTH and hydrocortisone.