Corticosteroid receptors in rat hippocampal sections: effect of adrenalectomy and corticosterone replacement

Rat brain sections, located at the hippocampal level, were used to study the effect of bilateral adrenalectomy, with or without corticosterone treatment, on the number and affinity of corticosteroid binding sites. Adrenalectomy induces an increase of corticosterone receptor binding sites whereas adrenalectomy followed by in vivo corticosterone treatment produces a 50% decrease of binding site number. Increases and decreases of binding site number were not associated with a significant modification of the affinity for corticosterone. The present data show that in vivo corticosterone modulates its own number of binding sites demonstrated by in vitro binding on brain sections, in a manner which is reminiscent of changes in cytosol receptors demonstrated by conventional biochemical methods. Thus, this in vitro method provides an alternative way to study the plasticity of hippocampal glucocorticoid receptors.