[3H]corticosterone binding in the caudate-putamen.

ABSTRACT

Autoradiographic data indicate little specific binding of corticosterone in the caudate-putamen. However, chronic glucocorticoid treatment has been reported to alter certain biochemical parameters within the caudate-putamen, including high-affinity choline uptake. We asked whether glucocorticoid receptors in the caudate-putamen of adrenalectomized rats could be detected by a biochemical approach. We determined the amount of specific [3H]corticosterone binding in cytosols from the caudate-putamen and the ability of nuclei in this brain region to retain [3H]corticosterone in vivo. Results indicated that 72 h post-adrenalectomy, the caudate-putamen has 56% of the maximal binding capacity of the hippocampus (205 +/- 11 vs 361 +/- 19 fmol/mg protein). The apparent Kd of [3H]corticosterone in the two tissues did not differ substantially. The cytosolic binding capacity of the caudate-putamen was similar to that of the cerebellum, a brain region which also fails to demonstrate marked retention of glucocorticoids in autoradiographic studies. When cytosol binding was measured at a shorter time period after adrenalectomy (12 h), no differences were observed between the binding capacities of the hippocampus and the caudate-putamen. In competition experiments using [3H]corticosterone as ligand, no differences between the caudate-putamen and the hippocampus were found in the relative affinities of any of 8 steroids; the order of relative affinities obtained was in good agreement with those reported for the classical glucocorticoid receptor in other tissues. Rats were injected via the tail vein with [3H]corticosterone, 36 nmol/kg, an amount calculated to saturate more than half the nuclear sites.(ABSTRACT TRUNCATED AT 250 WORDS)