Presynaptic Dopaminergic Dysfunction in Schizophrenia

Abstract

CONTEXT: The dopamine overactivity hypothesis of schizophrenia remains one of the most influential theories of the pathophysiology of the illness. Radiotracer brain imaging studies are now directly testing aspects of the overactivity hypothesis. OBJECTIVE: To assess presynaptic dopaminergic function in a large cohort of patients with schizophrenia by means of [18F]fluorodopa uptake and a high-sensitivity 3-dimensional positron emission tomograph. We predicted elevations in striatal [18F]fluorodopa uptake and reductions in prefrontal cortical [18F]fluorodopa uptake in patients with schizophrenia. DESIGN: Case-control study. SETTING: Research institute investigation recruiting hospital outpatients. PATIENTS: Sixteen male medicated hospital outpatients with a DSM-IV diagnosis of schizophrenia (mean age, 38 years) and 12 age-matched male volunteers free of psychiatric and neurologic illness. INTERVENTION: [18F]fluorodopa positron emission tomographic scanning. MAIN OUTDOME MEASURE: [18F]fluorodopa uptake constant Ki measured with statistical parametric mapping and region-of-interest analyses. RESULTS: Statistical parametric mapping (P<.05 corrected) and region-of-interest analyses (P<.01) showed increased [18F]fluorodopa uptake, confined primarily to the ventral striatum in patients with schizophrenia. No reductions in prefrontal cortical [18F]fluorodopa uptake Ki were seen in the statistical parametric mapping and region-of-interest analyses, although dorsal anterior cingulate [18F]fluorodopa Ki correlated with performance on the Stroop Color-Word Test in both groups. CONCLUSIONS: As in studies in unmedicated patients, presynaptic striatal dopamine dysfunction is present in medicated schizophrenic patients, adding further in vivo support for dopamine overactivity in the illness.