Extrastriatal D2 and striatal D2 receptors in depressive illness: Pilot PET studies using [11C]FLB 457 and [11C]raclopride

BackgroundReduced dopaminergic function may occur in depressive disorders. In this paper the results of two pilot studies examining different aspects of the dopamine system in depression are presented. First, the binding of [11C]FLB 457 to extrastriatal D2 receptors was measured in a group of depressed patients. Second, the hypothesis that selective serotonin reuptake inhibiting (SSRI) antidepressants affect the striatal binding of [11C]raclopride was tested.MethodsIn the first study the binding of [11C]FLB 457 was compared between 7 people with depression and 7 healthy controls. In the second study the binding of [11C]raclopride to striatal D2/3 receptors was compared between 8 people taking SSRI antidepressant medication and 8 healthy controls.ResultsThere was no difference in the binding of [11C]FLB 457 between the two groups. [11C]raclopride binding was reduced in the dorsal striatum of people taking antidepressants suggesting either that D2/3 expression was reduced, or that dopamine release was increased, compared to untreated controls.LimitationsThe depressed patients were not severely depressed and were not matched for gender with controls. In the raclopride group the patients and controls were not matched by gender and were taking different SSRI antidepressants.ConclusionWe found no support for the hypothesis that dopamine D2 receptor expression is altered in extrastriatal brain regions in depression. SSRI antidepressants were associated with reduced [11C]raclopride binding in the dorsal striatum supporting the hypothesis that therapeutic effects of such drugs may, in part, be due to changes in the dopamine system.