Several studies suggest that dysregulation of dopaminergic transmission in the midbrain and thalamus may contribute to the symptomatology of schizophrenia. The objective of this study was to examine the putative alteration of dopamine D(2/3 )receptor densities in the thalamus and midbrain of drug-naive schizophrenic patients. We used the high-affinity single-photon emission tomography ligand (123)Iepidepride for imaging D(2/3 )receptor binding sites in six neuroleptic-naive schizophrenic patients, and seven healthy controls. Schizophrenic symptoms were evaluated by the Positive and Negative Syndrome Scale. Significantly lower D(2/3 )values were observed in the midbrain of patients with schizophrenia compared to controls (P = 0.02). No statistically significant difference was observed in the thalamus between two groups. Negative correlations were found between thalamic D(2/3 )receptor binding and general psychopathological schizophrenic symptoms (r from -0.78 to -0.92). These observations implicate altered dopaminergic activity in the midbrain of schizophrenic patients.
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