Increased dopamine synthesis rate in medial prefrontal cortex and striatum in schizophrenia indicated by L-(β- 11C) DOPA and PET

Abstract

Background: The aim of the present study was to investigate dopamine synthesis in the brain of drug-free schizophrenic patients, not only in the striatum but also in extrastriatal areas like the prefrontal cortex, brain areas that for a long time has been in focus of interest in the pathophysiology of schizophrenia. Methods: PET was performed in 12 drug-free (10 drug-naive) psychotic schizophrenic patients and 10 healthy volunteers matched for age and gender using 11C-labelled l-DOPA as the tracer. The time-radioactivity curve from occipital cortex (located within Brodman area 17 and 18) was used as input function to calculate l-DOPA influx rate, K i images, that were matched to a common brain atlas. A significant overall increase of the K i values was found in the schizophrenic group as compared with healthy controls. Results: In particular, significantly higher K i were found in the schizophrenic patients compared to the controls in the caudate nucleus, putamen and in parts of medial prefrontal cortex (Brod 24). The K i value reflect an increased utilization of l-DOPA, presumably due to increased activity of the amino acid decarboxylate enzyme. Conclusions: The results indicate that the synthesis of dopamine is elevated within the striatum and parts of medial prefrontal cortex in schizophrenia.