The effects of adrenalectomy and thermal stress on glutamic acid decarboxylase activity in different regions of the rat brain

Glutamic acid decarboxylase (GAD) enzyme activity was measured in synaptosomes prepared from the hypothalamus, the hippocampus, the striatum and the cerebral cortex of control, adrenalectomized and rat exposed to a thermal stress. Adrenalectomy caused a statistically significant decrease in the enzyme activity in the striatum, while it had no effect in the other three brain areas. On the other hand, exposure to the thermal stress resulted in a dramatic increase of GAD specific activity in all brain areas examined. This thermal stress-induced increase in enzyme activity was observed in both non-operated and adrenalectomized animals, which implies that it is not mediated by glucocorticoids. © 1991 Plenum Publishing Corporation

Stress Affects the Activated Form of the Corticosteroid‐Receptor Complex in the Rat Brain

Glucocorticoid actions in the brain, particularly in the hippocampus and the hypothalamus, are critically involved in the response of the organism to stress. The key molecules in this process are the corticosteroid receptors, which upon activation, migrate and act in the nucleus. We have investigated the effect of stress on the activated form of the cytosolic glucocorticoid receptor from the above brain areas, using anion exchange chromatography. Exposure of rats to chronic stress resulted in the disappearance of the chromatographic peak, which corresponds to the activated form (DE II) of the hormone‐receptor complex. For this phenomenon to occur, 1) the animal must be exposed to chronic, and not to acute stress, and 2) the adrenals of the animal must be intact. The disappearance of the activated form of the hormone‐receptor complex (DE II) following chronic stress is most probably due to proteolysis of the receptor molecule, since it is specifically inhibited by the protease inhibitor leupeptin. This phenomenon may represent an adaptive mechanism which helps the organism cope with a repeated stressor. Copyright © 1992, Wiley Blackwell. All rights reserve