Glutamate receptors mediate most excitatory neurotransmission in the brain and play an important role in neural plasticity, neural development and neurodegeneration . Ionotropic glutamate receptors are categorized into NMDA receptors and kainate/AMPA receptors, both of which contain glutamate-gated, caution-specific ion channels . Kainate/AMPA receptors are co-localized with NMDA receptors in many synapses and consist of seven structurally related subunits designated GluR-1 to -7 . The kainate/AMPA receptors are primarily responsible for the fast excitatory neurotransmission by glutamate whereas the NMDA receptors are functionally characterized by a slow kinetic and a high permeability for Ca2+ ions . The NMDA receptors consist of five subunits: epsilion 1, 2, 3, 4 and one zeta subunit . The zeta subunit is expressed throughout the brainstem, whereas the four epsilon subunits display limited distribution.Synonyms: GRIN2D, Glutamate [NMDA] receptor subunit epsilon-4, N-methyl D-aspartate receptor subtype 2D, NMDAR2D, NR2D