Amino Acid Neurotransmitters Assessed by Proton Magnetic Resonance Spectroscopy: Relationship to Treatment Resistance in Major Depressive Disorder

Rebecca B. Price, Dikoma C. Shungu, Xiangling Mao, Paul Nestadt, Chris Kelly, Katherine A. Collins, James W. Murrough, Dennis S. Charney, Sanjay J. Mathew

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Significant alterations in γ-aminobutyric acid (GABA) and glutamate levels have been previously reported in major depressive disorder (MDD); however, no studies to date have investigated associations between these amino acid neurotransmitters and treatment resistance. Methods: The objective of this study was to compare occipital cortex (OCC) and anterior cingulate cortex (ACC) GABA and glutamate+glutamine (Glx) levels measured by proton magnetic resonance spectroscopy (1H MRS) in 15 medication-free treatment-resistant depression (TRD) patients with those in 18 nontreatment-resistant MDD (nTRD) patients and 24 healthy volunteers (HVs). Results: Levels of OCC GABA relative to voxel tissue water (W) were decreased in TRD patients compared with both HV (20.2% mean reduction; p = .001; Cohen's d = 1.3) and nTRD subjects (16.4% mean reduction; p = .007; Cohen's d = 1.4). There was a similar main effect of diagnosis for ACC GABA/W levels (p = .047; Cohen's d = .76) with TRD patients exhibiting reduced GABA in comparison with the other two groups (22.4% to 24.5% mean reductions). Group differences in Glx/W were not significant in either brain region. Only GABA results in OCC survived correction for multiple comparisons. Conclusions: Our findings corroborate previous reports of decreased GABA in MDD and provide initial evidence for a distinct neuronal amino acid profile in patients who have failed to respond to several standard antidepressants, possibly indicative of abnormal glutamate/glutamine/GABA cycling. Given interest in novel antidepressant mechanisms in TRD that selectively target amino acid neurotransmitter function, the translational relevance of these findings awaits further study.

Original languageEnglish (US)
Pages (from-to)792-800
Number of pages9
JournalBiological psychiatry
Volume65
Issue number9
DOIs
StatePublished - May 1 2009
Externally publishedYes

Keywords

  • Depression
  • GABA
  • glutamate
  • magnetic resonance
  • spectroscopy

ASJC Scopus subject areas

  • Biological Psychiatry

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