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Neuroinflammation in Schizophrenia-Related Psychosis: A PET Study

¹ Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; ² Department of Radiology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands; and ³ University Center of Psychiatry, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands

Correspondence: For correspondence or reprints contact: Janine Doorduin, Department of Nuclear Medicine and Molecular Imaging, University Medical Center Groningen, University of Groningen, P.O. Box 30.001, 9700 RB Groningen, The Netherlands. E-mail: j.doorduin{at}ngmb.umcg.nl

Schizophrenia is a chronic and disabling brain disease characterized by psychotic episodes with unknown etiology. It is suggested that neuroinflammation plays a role in the pathophysiology of schizophrenia. Neuroinflammation is characterized by the activation of microglia cells, which show an increase in the expression of the peripheral benzodiazepine receptor. The isoquinoline (R)-N-¹¹C-methyl-N-(1-methylpropyl)-1-(2-chlorophenyl)isoquinoline-3-carboxamide (¹¹C-(R)-PK11195) is a peripheral benzodiazepine receptor ligand that can be used for the imaging of activated microglia cells, and thus neuroinflammation, with PET. We hypothesized that neuroinflammation would be more profound in schizophrenic patients during psychosis, and it was therefore investigated whether neuroinflammation was present in patients within the schizophrenia spectrum who were in a psychotic phase. Methods: Seven patients within the schizophrenia spectrum who were recovering from psychosis were included. Recovering psychosis was defined by a score of 5 or more on 1 item of the positive scale of the positive and negative symptoms scale (PANSS) or a score of 4 on 2 items. The patients were compared with 8 age-matched healthy volunteers. Dynamic 60-min PET scans were acquired after the injection of ¹¹C-(R)-PK11195. All subjects underwent T1- and T2-weighted MRI, and the scans were visually examined for abnormalities and used for anatomic coregistration in data analysis. The PET data were analyzed with a 2-tissue-compartment model to calculate the binding potential, using the metabolite-corrected plasma curve as input. Results: A significantly higher binding potential of ¹¹C-(R)-PK11195, indicative of neuroinflammation, was found in the hippocampus of schizophrenic patients than in healthy volunteers (2.07 ± 0.42 vs. 1.37 ± 0.30; P = 0.004). A nonsignificant 30% higher ¹¹C-(R)-PK11195 binding potential was found in the whole-brain gray matter of schizophrenic patients. The MR images did not reveal any visual abnormalities. Conclusion: The present study suggests that focal neuroinflammation may play an important role in schizophrenia during psychosis.

Key Words: schizophrenia • psychosis • neuroinflammation • microglia • PET • ¹¹C-PK11195

COPYRIGHT © 2009 by the Society of Nuclear Medicine, Inc.

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JNM 2009 50: 11A-12A. [Full Text]