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Neuropsychopharmacology. 2016 Sep;41(10):2606-13. doi: 10.1038/npp.2016.84. Epub 2016 Jun 8.

Glutamatergic Metabolites, Volume and Cortical Thickness in Antipsychotic-Naive Patients with First-Episode Psychosis: Implications for Excitotoxicity.

Author information

1
Multimodal Imaging Group, Research Imaging Centre, Centre for Addiction and Mental Health, University of Toronto, Toronto, ON, Canada.
2
Institute of Medical Science, University of Toronto, Toronto, ON, Canada.
3
Cerebral Imaging Centre, Douglas Mental Health University Institute, McGill University, Montreal, QC, Canada.
4
Departments of Psychiatry and Biomedical Engineering, McGill University, Montreal, QC, Canada.
5
Kimel Family Translational Imaging-Genetics Research Laboratory, Research Imaging Centre, Centre for Addiction and Mental Health, University of Toronto, Toronto, ON, Canada.
6
Department of Psychiatry, University of Toronto, Toronto, ON, Canada.
7
Laboratory of Experimental Psychiatry, Instituto Nacional de Neurología y Neurocirugía, Mexico City, Mexico.
8
Department of Education, Instituto Nacional de Neurología y Neurocirugía, Mexico City, Mexico.
9
Neuropsychiatry Department, Instituto Nacional de Neurología y Neurocirugía, Mexico City, Mexico.
10
Geriatric Mental Health Division, Centre for Addiction and Mental Health, University of Toronto, Toronto, ON, Canada.
11
Campbell Institute Research Program, Centre for Addiction and Mental Health, University of Toronto, Toronto, ON, Canada.

Abstract

Neuroimaging studies investigating patients with schizophrenia often report appreciable volumetric reductions and cortical thinning, yet the cause of these deficits is unknown. The association between subcortical and cortical structural alterations, and glutamatergic neurometabolites is of particular interest due to glutamate's capacity for neurotoxicity; elevated levels may be related to neuroanatomical compromise through an excitotoxic process. To this end, we explored the relationships between glutamatergic neurometabolites and structural measures in antipsychotic-naive patients experiencing their first non-affective episode of psychosis (FEP). Sixty antipsychotic-naive patients with FEP and 60 age- and sex-matched healthy controls underwent a magnetic resonance imaging session, which included a T1-weighted volumetric image and proton magnetic resonance spectroscopy in the precommissural dorsal caudate. Group differences in precommissural caudate volume (PCV) and cortical thickness (CT), and the relationships between glutamatergic neurometabolites (ie, glutamate+glutamine (Glx) and glutamate) and these structural measures, were examined. PCV was decreased in the FEP group (p<0.001), yet did not differ when controlling for total brain volume. Cortical thinning existed in the FEP group within frontal, parietal, temporal, occipital, and limbic regions at a 5% false discovery rate. Glx levels were negatively associated with PCV only in the FEP group (p=0.018). The observed relationship between Glx and PCV in the FEP group is supportive of a focal excitotoxic mechanism whereby increased levels of glutamatergic markers are related to local structural losses. This process may be related to the prominent structural deficits that exist in patients with schizophrenia.

PMID:
27272768
PMCID:
PMC4987861
DOI:
10.1038/npp.2016.84
[Indexed for MEDLINE]
Free PMC Article

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