GRIN2B and major depressive disorder: Also, NMDA (N-methyl-D-Aspartate) receptors Grin2a (Glutamate receptor ionotropic, NMDA 2A) and Grin2b (Glutamate receptor ionotropic, NMDA 2B) play key role in the pathology of mood disorders and their polymorphisms could be associated with depression [69].