Neurotransmitters and Neurometabolites in Late-Life Depression: A Preliminary Magnetic Resonance Spectroscopy Study at 7T

Abstract Background Magnetic resonance spectroscopy (MRS) methods have quantified changes in levels of neurotransmitters and other neurometabolites in patients with major depression across the lifespan. 7T field strengths and greater have not been a major focus of study in patients with late-life depression (LLD). Methods Nine LLD patients who met DSM-IV criteria for a current major depressive episode and nine non-depressed, healthy, age-matched controls underwent clinical and neuropsychological assessment and single-voxel 7T 1H-MRS at baseline and after 10-12 weeks of antidepressant treatment (Citalopram; patients only). Spectra were acquired from two brain regions implicated in both depressive symptoms and neuropsychological deficits in LLD, the anterior (ACC) and posterior cingulate (PCC). Levels of γ-aminobutyric acid (GABA), glutamate (Glu), glutathione (GSH), N-acetylaspartylglutamate (NAAG), N-acetylaspartate (NAA), and myo-inositol (mI) were quantified relative to total creatine (tCr) using linear-combination modeling. Results Baseline Glu/tCr levels were not significantly different between groups. Decreased Glu/tCr levels levels after Citalopram treatment was observed in a subset of LLD patients, although the group difference was not statistically significant. Exploratory analyses showed that LLD patients had lower NAA levels in the PCC relative to controls. Higher levels of ml in the LLD patients relative to the controls and decreases after Citalopram treatment had large effect sizes but were not statistically significant. Further, decreases in PCC Glu/tCr and increases in ACC GSH/tCr were associated with improvement in depressive symptoms. Limitations Sample size. Conclusions These preliminary results suggest a role of neurochemicals and neurometabolites in the neurobiology of LLD and antidepressant treatment response.