Benzodiazepine receptors in rat brain are altered by adrenalectomy

The effects of adrenalectomy on benzodiazepine receptors in discrete regions of rat brain were examined using [3H]flunitrazepam as binding ligand. The concentration of benzodiazepine receptors was significantly increased by 25, 50 and 71% in hippocampus, striatum and hypothalamus, respectively, after adrenalectomy. In contrast, adrenalectomy did not affect the concentration of benzodiazepine receptors in cerebral cortex, olfactory bulb and cerebellum. No significant differences in the apparent binding affinity (Kd) values were seen following adrenalectomy in any brain region examined. The adrenalectomy-induced increases in [3H]flunitrazepam binding sites were completely reversed by glucocorticoid replacement with dexamethasone. These results demonstrate that adrenalectomy is capable of selectively modulating benzodiazepine receptors in brain regions presumably involved with glucocorticoid negative feedback. The data further suggest additional mechanisms by which endogenous hypothalamic-pituitary-adrenocortical hormones may affect 'anxiety' levels.