N-methyl-D-aspartate receptors (NMDARs) are ligand-gated ionotropic glutamate receptors that mediate excitatory synaptic transmission and play important roles in many aspects of nervous system function including: synaptic plasticity; learning and memory; neuronal development and circuit formation. NMDARs have been implicated in various neuronal disorders. NMDARs are heteromers consisting of an obligate NR1 subunit and most commonly one or two kinds of NR2 subunits or occasionally NR3 subunits.

The NR1 subunit is alternatively spliced yielding eight possible isoforms characterised by the inclusion or deletion of exons 5, 21 and 22. The splice variants are developmentally and spatially regulated and modulate the biophysical properties of NMDARs and alter the trafficking behaviour of NR1.
NR1-4b Splice variants includes exons 5, 21, and 22 and is expressed in the dorsal horn of the spinal cord.

The involvement of NMDAR in the central nervous system (CNS) has become a focus area for neurodegenerative diseases such as Alzheimer’s disease, epilepsy and ischemic neuronal cell death.