UPTAKE OF CORTICOSTERONE BY RAT BRAIN AND ITS CONCENTRATION BY CERTAIN LIMBIC STRUCTURES

[1,2-3H] Corticosterone is taken up by all parts of the brain of normal and adrenalectomized rats. As the blood concentration of hormone increases, a situation which occurs following stress, the concentration of hormone in the brain also increases. Superimposed on top of the brain-wide uptake of corticosterone is the tendency of 2 limbic structures, the hippocampus and septum, to concentrate and retain labeled corticosterone. The hippocampal uptake sites are saturated by levels of corticosterone found in normal rats, while the septal sites are not. Hippocampal uptake is therefore observed only in adrenalectomized rats and can be seen as early as 2 h after adrenalectomy. The hippocampal uptake sites in adrenalectomized rats are saturated by exogenous unlabeled corticosterone, hydrocortisone, and dexamethasone. The relevance of hormone retention to the function of the hippocampus and septum in behavior and control of ACTH release is discussed. The possible cellular sites of action of corticosterone are also considered. © 1969.