Brain adrenergic receptors and resistance to stress.

The relationship between brain beta-adrenergic receptors and adaptation to stress was studied in rats subjected to repeated restraint stress. The stress was found to produce a reduction in the density of these receptors in the hypothalamus, cerebral cortex and brain stem. This change first appeared after 4-7 days and persisted for the duration of the two-week stress. Adaptation, as judged by resistance to the anorexic and gastric lesion-inducing effects of the stress, occurred progressively over the full two-week period. The loss of beta-receptors was found to correlate positively with the degree of adaptation. The relationship was strongest for the hypothalamus but was also apparent in the cortex and brain stem. These findings support the hypothesis that a reduction in the number of brain adrenergic receptors is one of the biochemical factors underlying adaptation to stress.