Electroconvulsive shock but not antidepressant drugs increases alpha 1-adrenoceptor binding sites in rat brain

Treatment of rats with electroconvulsive shock once daily for 10-12 days increased the density of alpha 1-adrenoceptors labeled by [3H]prazosin in homogenates of frontal cerebral cortex. A single treatment did not affect [3H]prazosin binding. Repeated treatment with electroconvulsive shock did not appear to affect alpha 1-adrenoceptor binding in the hippocampus or hypothalamus. Treatment of rats with reserpine also increased [3H]prazosin binding in the frontal cortex. In contrast to electroconvulsive shock, three weeks administration of tricyclic antidepressant drugs, monoamine oxidase inhibitors, or atypical antidepressant drugs did not significantly affect [3H]prazosin binding sites in the frontal cortex. The affinities of antidepressant drugs for alpha 1-adrenoceptors ranged from about 50 nM for tricyclic and atypical antidepressants to about 100 microM for monoamine oxidase inhibitors. The high affinities of the tricyclic and atypical antidepressant drugs for alpha 1-adrenoceptors could contribute to clinical differences between these classes of drugs and monoamine oxidase inhibitors. Furthermore, the electroconvulsive shock-induced increase in alpha 1-adrenoceptors could contribute to differences in clinical effects between this treatment and antidepressant drugs.