Extrastriatal and striatal D(2) dopamine receptor blockade with haloperidol or new antipsychotic drugs in patients with schizophrenia.

Abstract

Both traditional and atypical antipsychotics have been hypothesised to be effective in schizophrenia through limbic and cortical D(2) dopamine receptor blockade. To investigate this hypothesis with the D(2)/D(3)-selective positron emission tomography (PET) probe [(76)Br]-FLB457. PET scans were performed on 6 controls and 18 patients with schizophrenia treated with haloperidol or with risperidone, clozapine, amisulpride or olanzapine. The D(2) dopamine receptor blockade was high in the temporal cortex with both haloperidol and atypical antipsychotics. The atypicals, however, induced a significantly lower D(2) binding index than haloperidol in the thalamus and in the striatum. Results suggest that cortical D(2) dopamine receptors are a common target of traditional and atypical antipsychotics for therapeutic action. Higher in vivo binding to the D(2) receptors in the cortex than in the basal ganglia is suggested as an indicator of favourable profile for a putative antipsychotic compound.