EFFECTS OF CHRONIC ANTIDEPRESSANT TREATMENT ON BETA-ADRENOCEPTOR SUBTYPE BINDING IN THE RAT CEREBRAL-CORTEX AND CEREBELLUM

The effects of desipramine, tranylcypromine, and phenelzine on beta-ad renoceptor subtype binding were measured in rat cerebral cortex and ce rebellum. The drugs were administered to male Sprague Dawley rats for 28 d sc via 2ML4 Alzet osmotic minipumps (desipramine HCI 10, tranylcy promine HCI 1, phenelzine sulfate 5, 10 mg kg-1/d). Binding of [H-3]CG P 12177 was measured to determine total beta-adrenoceptor density in e ach brain region. The relative densities of beta1- and beta2-adrenocep tors were directly calculated from competition analysis using ICI 8940 6 to displace [H-3]CGP 12177. Beta1-Adrenoceptor density was decreased in cortical tissue following each antidepressant treatment, but no ef fects on beta2-adrenoceptor density were evident. With cerebellar tiss ue, despite a higher density of beta2-adrenoceptors in this area, no e ffects of antidepressants on beta2-adrenoceptor density were evident. The present data confirm and extend previous reports of beta1- but not beta2-adrenoceptor downregulation in brain following chronic antidepr essant drug treatment.