Mechanisms of the analgesic effect of corticotropin-releasing factor in conscious rats

摘要

We report here our studies of the contribution of the hypothalamo- hypophyseal-adrenocortical system (HHACS) and opioid system to the analgesic effect of corticotropin-releasing factor (CRF) in conscious rats exposed to thermal stimuli. Two methodological approaches were used: 1) blockade of the functional activity of the HHACS by administration of hydrocortisone at a pharmacological dose one week before experiments; 2) blockade of glucocorticoid receptors with the glucocorticoid receptor antagonist RU38486. The contribution of the opioid system was studied by blockade of opioid receptors with their antagonist naltrexone. Blockade of opioid receptors completely eliminated the analgesic effect of CRF, blockade of the functional activity of the HHACS decreased it, and blockade of glucocorticoid receptors increased the effect. These data provide evidence that the analgesic effect of CRF in conscious rats exposed to a thermal stimulus is mediated by an opioid-associated mechanism. The actions of opioids on pain sensitivity may be modulated by glucocorticoid hormones.