• dorsolateral prefrontal cortex;
  • major depressive disorder;
  • myoinositol;
  • N-acetyl aspartate;
  • proton magnetic resonance spectroscopy

Aim:  Recent neuroimaging studies support functional and structural alterations in the dorsolateral prefrontal cortex (DLPFC), particularly on the left side in patients with major depressive disorders (MDD). The aim of the present study was to examine the biochemical characteristics of left DLPFC as measured on proton (1H) magnetic resonance spectroscopy (MRS) in patients with drug-naïve first-episode MDD and a healthy control group. A second aim was to assess the effect of antidepressant treatment on the metabolites of DLPFC.

Methods:  Short-echo single-voxel 1H-MRS was done for the left DLPFC in 17 female drug-free MDD patients (mean age ± SD, 30.9 ± 6.9 years) and 13 matched control subjects (mean age ± SD, 29.1 ± 6.2 years) and was repeated at 8 weeks following antidepressant treatment.

Results:  Comparison of baseline values indicated that there were no significant differences in any of the metabolite ratios (N-acetyl aspartate/creatine [NAA/Cr], myoinositol [Ino]/Cr, and choline [Cho]/Cr) between patients and controls. Significant differences were detected between pre- and post-treatment Ino/Cr ratios (0.67 ± 0.13, 0.58 ± 0.22, P = 0.032, respectively), although there was no difference in NAA/Cr and Cho/Cr ratios.

Conclusion:  Although no significant metabolic alterations exist in female patients with drug-naïve first-episode MDD as evaluated on 1H-MRS, an increase in Ino/Cr was observed following 8-week antidepressant treatment. These findings give rise to the possibility that non-neuronal cells, particularly glial cells that are probably damaged, play a role in the action of antidepressant treatment.