The international journal of neuropsychopharmacology
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Int. J. Neuropsychopharmacol. · Sep 2012
An investigation of amino-acid neurotransmitters as potential predictors of clinical improvement to ketamine in depression.
Amino-acid neurotransmitter system dysfunction plays a major role in the pathophysiology of major depressive disorder (MDD). We used proton magnetic resonance spectroscopy (¹H-MRS) to investigate whether prefrontal levels of amino-acid neurotransmitters predict antidepressant response to a single intravenous infusion of the N-methyl-D-aspartate (NMDA) antagonist ketamine in MDD patients. Fourteen drug-free patients with MDD were scanned 1-3 d before receiving a single intravenous infusion of ketamine (0.5 mg/kg). ⋯ Pretreatment glutamate levels in the VM-PFC were positively correlated with improvement in anxiety symptoms [r s(11)=0.57, p<0.05]. The findings suggest an association between lower Glx/glutamate ratio and greater improvement in response to ketamine treatment. Because glutamine is mainly contained in glia, the decreased Glx/glutamate ratio observed in this study may reflect the reduction in glial cells found in the same regions in post-mortem studies of individuals with MDD, and suggests that the presence of this neuropathological construct may be associated with antidepressant responsiveness to ketamine.