Striatal and extra-striatal D2/D3 dopamine receptor occupancy by quetiapine in vivo

Abstract

BackgroundSelective action at limbic cortical dopamine D2-like receptors could mediate atypical antipsychotic efficacy with few extrapyramidal side-effects.AimsTo test the hypothesis that quetiapine has ‘limbic selective’ D2/D3 receptor occupancy in vivo.MethodThe high-affinity D2/D3 ligand [123I]-epidepride and single photon emission tomography were used to estimate D2/D3 specific binding and an index of relative percentage D2/D3 occupancy in striatal and temporal cortical regions for quetiapine-treated patients (n=6). Quetiapine-, and previously studied typical-antipsychotic- and clozapine-treated patients were compared.ResultsMean (s.d.) relative percentage D2/D3 receptor occupancy by quetiapine was 32.0% (14.6) in striatum and 60.1% (17.2) in temporal cortex (mean daily dose 450 mg: range 300–700 mg/day). Quetiapine treatment resulted in limbic selective D2/D3 blockade similar to clozapine and significantly higher than typical antipsychotics.ConclusionsPreliminary data suggest that limbic selective D2/D3 receptor blockade is important for atypical drug action.