Corticosterone treatment differentially affects adrenocorticoid receptors expression and binding in the hippocampus and Spinal Cord of the Rat

We have studied the immediate and long-term effects of high doses of corticosterone (CORT) on mRNA expression and binding properties of mineralocorticoid receptor and glucocorticoid receptor in the hippocampus and spinal cord of rats. Animals were treated with corticosterone (10 mg/d subcutaneously) for 21 consecutive days, and mineralocorticoid and glucocorticoid receptors were studied either 24 h or 2 wk after the last injection. Major results show that corticosterone treatment reduces mineralocorticoid and glucocorticoid receptor maximum binding capacity (Bmax) in both the hippocampus and spinal cord and that this reduction is partially reversed after cessation of treatment. With respect to mRNA expression, in the hippocampus recovery after cessation of treatment is complete. By contrast, in the spinal cord, mineralocorticoid receptor mRNA expression is irreversibly increased after treatment, but the glucocorticoid receptor mRNA level remains unaffected during and after treatment. Thus, these data suggest the presence of distinct regulatory mechanisms for adrenocorticoid receptors in rat brain and spinal cord, in response to long-term exposure to high levels of circulating corticosterone and after recovery from treatment.