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 c orticosterone (CORT) on mRNA expression and binding properties of mine ralocorticoid 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 an d glucocorticoid receptors were studied either 24 h or 2 wk after the last injection. Major results show that corticosterone treatment reduc es mineralocorticoid and glucocorticoid receptor maximum binding capac ity (B-max) in both the hippocampus and spinal cord and that this redu ction is partially reversed after cessation of treatment. With respect to mRNA expression, in the hippocampus recovery after cessation of tr eatment is complete. By contrast, in the spinal cord, mineralocorticoi d receptor mRNA expression is irreversibly increased after treatment, but the glucocorticoid receptor mRNA level remains unaffected during a nd after treatment. Thus, these data suggest the presence of distinct regulatory mechanisms for adrenocorticoid receptors in rat brain and s pinal cord, in response to long-term exposure to high levels of circul ating corticosterone and after recovery from treatment.