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

Background: The aim of the present study was to investigate dopamine synthe sis in the brain of drug-free schizophrenic patients, not only in the stria tum 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 schizo phrenic patients and 10 healthy volunteers matched for age and gender using C-11-labelled L-DOPA as the tracer The time-radioactivity curve from occip ital cortex (located within Brodman area 17 and 18) was used as input funct ion to calculate L-DOPA influx rate, K-i images, that were matched to a com mon 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 schizoph renic 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 i ncreased 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 elevate d within the striatum and parts of medial prefrontal cortex in schizophreni a. Biol Psychiatry 1999;46:681-688 (C) 1999 Society of Biological Psychiatr y.