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Neuropsychopharmacology. 2018 Sep;43(10):2154-2160. doi: 10.1038/s41386-018-0136-3. Epub 2018 Jun 28.

The effects of ketamine on prefrontal glutamate neurotransmission in healthy and depressed subjects.

Author information

1
Clinical Neurosciences Division, National Center for PTSD, US Department of Veterans Affairs, West Haven, CT, USA. chadi.abdallah@yale.edu.
2
Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA. chadi.abdallah@yale.edu.
3
Department of Radiology and Biomedical Imaging, Yale Magnetic Resonance Research Center, Yale University School of Medicine, New Haven, CT, USA.
4
Clinical Neurosciences Division, National Center for PTSD, US Department of Veterans Affairs, West Haven, CT, USA.
5
Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA.
6
Department of Biomedical Engineering, Columbia University, New York, NY, USA.
7
Department of Radiology, Columbia University, New York, NY, USA.
8
Department of Neurology, Yale University School of Medicine, New Haven, CT, USA.

Abstract

The ability of ketamine administration to activate prefrontal glutamate neurotransmission is thought to be a key mechanism contributing to its transient psychotomimetic effects and its delayed and sustained antidepressant effects. Rodent studies employing carbon-13 magnetic resonance spectroscopy (13C MRS) methods have shown ketamine and other N-methyl-D-aspartate (NMDA) receptor antagonists to transiently increase measures reflecting glutamate-glutamine cycling and glutamate neurotransmission in the frontal cortex. However, there are not yet direct measures of glutamate neurotransmission in vivo in humans to support these hypotheses. The current first-level pilot study employed a novel prefrontal 13C MRS approach similar to that used in the rodent studies for direct measurement of ketamine effects on glutamate-glutamine cycling. Twenty-one participants (14 healthy and 7 depressed) completed two 13C MRS scans during infusion of normal saline or subanesthetic doses of ketamine. Compared to placebo, ketamine increased prefrontal glutamate-glutamine cycling, as indicated by a 13% increase in 13C glutamine enrichment (t = 2.4, p = 0.02). We found no evidence of ketamine effects on oxidative energy production, as reflected by 13C glutamate enrichment. During ketamine infusion, the ratio of 13C glutamate/glutamine enrichments, a putative measure of neurotransmission strength, was correlated with the Clinician-Administered Dissociative States Scale (r = -0.54, p = 0.048). These findings provide the most direct evidence in humans to date that ketamine increases glutamate release in the prefrontal cortex, a mechanism previously linked to schizophrenia pathophysiology and implicated in the induction of rapid antidepressant effects.

PMID:
29977074
PMCID:
PMC6098048
DOI:
10.1038/s41386-018-0136-3
[Indexed for MEDLINE]
Free PMC Article

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