Behavioral, Physiological and Neurochemical Charges Induced by Psychological Stress in Rats*

Abstract

Rats which could not escape and/or avoid shock developed more gastric ulceration than did escapable rats which had exactly the same shock but could exert control over shock. The inescapable rats also displayed sustained increases in norepinephrine (NE) turnover in the hypothalamus, amygdala and thalamus regardless of stress durations. When the escapable rats had firmly mastered the coping response, on the other hand, excess NE utilization at the earlier stage of stress was reduced in these brain regions. These findings suggested that absence of control over a stressor (i.e., uncontrollability) produced debilitating physiological and/or neurochemical changes. Rats receiving unsignalled shocks exhibited larger stomach ulcers than did no-shock and signalled-shock rats. Assay of regional brain NE turnover revealed that unsignalled shocks resulted in enhancements of NE turnover in the hypothalamus, amygdala, thalamus, midbrain, cerebral cortex and locus coeruleus region, as compared with the signalled shocks. The results suggested that both control and prediction are psychologically and biologically important factors in determining behavioral, physiological or neurochemical changes induced by stress.