GRIN2B gene expression is increased in the anterior cingulate cortex in major depression

The glutamatergic system may be central to the neurobiology and treatment of major depressive disorder (MDD) and psychosis. Despite the success of N-methyl-D-aspartate receptor (NMDAR) antagonists for the treatment of MDD, little is known regarding the expression of these glutamate receptors in MDD. In this study we measured gene expression, via qRT-PCR, of the major NMDAR subunits, in the anterior cingulate cortex (ACC) in MDD subjects with and without psychosis, and non-psychiatric controls. Overall, GRIN2B mRNA was increased in both MDD with (+32%) and without psychosis (+40%) compared to controls along with a trend increase in GRIN1 mRNA in MDD overall (+24%). Furthermore, in MDD with psychosis there was a significant decrease in the GRIN2A:GRIN2B mRNA ratio (-19%). Collectively these results suggest dysfunction of the glutamatergic system at the gene expression level in the ACC in MDD. Increased GRIN2B mRNA in MDD, along with an altered GRIN2A:GRIN2B ratio in psychotic depression, suggests a disruption to NMDAR composition could be present in the ACC in MDD; this could lead to enhanced signalling via GluN2B-containing NMDARs and greater potential for glutamate excitotoxicity in the ACC in MDD. These results support future research into GluN2B antagonist-based treatments for MDD.