Chronic glucocorticoid deficiency-induced abnormal aggression, autonomic hypoarousal, and social deficit in rats

Certain aggression-related psychopathologies are associated with decreased glucocorticoid production and autonomic functions in humans. We have previously shown that experimentally-induced chronic glucocorticoid deficiency leads to abnormal forms of attack in rats. Here, we compared the effects of acute and chronic glucocorticoid deficiency on aggressive behaviour, autonomic responses to challenges, and anxiety. Glucocorticoid synthesis was blocked acutely by the glucocorticoid synthesis blocker metyrapone or chronically by adrenalectomy and low glucocorticoid replacement (ADXr). As shown previously, chronic glucocorticoid deficiency facilitated aberrant attacks directed towards the most vulnerable parts of the opponent's body. The acute inhibition of glucocorticoid synthesis lowered aggressive behaviour without affecting attack targeting. In a different experiment, ADXr rats and their sham-operated controls were exposed to different challenges whereas their heart rate and locomotion were telemetrically recorded. Autonomic responses to social challenges were lowered by chronic, but not by acute glucocorticoid deficiency. Autonomic responses to the elevated plus-maze were only slightly affected by chronic glucocorticoid deficiency. Locomotor behaviour was not affected in either challenge; thus, the altered autonomic reactions were not due to interference from workload. The behaviour of ADXr rats was similar to that of sham-operated controls in the elevated plus-maze, but ADXr rats showed reduced social interactions in the social interaction test. Our data demonstrate that, in rats, chronic but not acute glucocorticoid deficiency induces abnormal attack patterns, deviant cardiovascular responses and social deficits that are similar to those seen in abnormally violent humans. Thus, the similar correlations found in humans probably cover a causal relationship. Experimentally-induced glucocorticoid deficiency may be used to assess the mechanisms underlying glucocorticoid deficiency-induced abnormal forms of aggressiveness.