MONOAMINE RECEPTORS IN AN ANIMAL-MODEL OF AFFECTIVE-DISORDER

Abstract: After a relatively mild course of uncontrollable shocks, two distinct groups of rats can be defined in terms of their performance in learning to escape from a controllable stressor. Response‐deficient (RD) rats do not learn to terminate the controllable stressor, whereas nondeficient (ND) rats learn this response as readily as do untreated control rats. The current studies were designed to determine the neu‐rochemical correlates of the behavioral differences between these groups of rats. The major findings concerned postsyn‐aptic β‐adrenergic effects in the hippocampus of RD rats. These included an up‐regulation of β‐adrenergic receptors and, in parallel experiments, an increase in the sensitivity of adenylyl cyclase to stimulation by norepinephrine. There was no difference in brain levels of catecholamines between the three groups of rats. A statistically significant increase in levels of 5‐hydroxytryptamine was noted in the hippocampus and hypothalamus of RD rats as compared to levels in ND rats, but no significant differences were measured between groups of rats in terms of S1 or S2 serotonergic receptor binding. These results implicate both β‐adrenergic and serotonergic mechanisms in the behavioral deficit caused by uncontrollable shock. Copyright © 1990, Wiley Blackwell. All rights reserved