Myo-inositol, Glutamate, and Glutamine in the Prefrontal Cortex, Hippocampus, and Amygdala in Major Depression

Abstract

Background: The brains of patients with depression exhibit many changes in various regions. Recently, proton magnetic resonance spectroscopy has been used to measure brain metabolites, using saturation bands to shape the volume of interest. Our a priori hypothesis was that myo-inositol and glutamate were downregulated in the hippocampus and amygdala in depression.

Methods: We measured brain metabolites from the medial prefrontal cortex, hippocampus, and amygdala of 22 drug-naïve, first-episode patients with major depressive disorder and 27 healthy control subjects using 3T proton magnetic resonance spectroscopy.

Results: Compared with healthy control subjects, patients showed statistically significant reductions in myo-inositol levels in all three regions and reductions in glutamate levels in the medial prefrontal cortex. Furthermore, we found significant decreases in the ratios of glutamate to creatine plus phosphocreatine in the medial prefrontal cortex and amygdala. Additionally, the ratios of glutamine to creatine plus phosphocreatine were also decreased in all three regions examined, although not all the participants presented reliable data. Finally, glutamate levels in the medial prefrontal cortex and amygdala have significant correlations with executive function and those in the hippocampus with memory function. Hippocampal myo-inositol was significantly related to blood cortisol.

Conclusions: Our findings indicated abnormal myo-inositol, glutamate, and glutamine levels in the brains of major depressive disorder patients.

Keywords: Amygdala; Depression; Glutamate; Glutamine; Hippocampus; Myo-inositol.