NMDA (N-Methyl-D-Aspartate) receptors are a type of specialized glutamate receptors belonging to the ion channel protein family. These receptors are formed by the assembly of NR1, NR2 (A-D), and NR3 (A-B) subunits into heterotetramers. They are primarily located in the central nervous system, especially on the postsynaptic membranes of neurons. NMDA receptors are involved in various biological reactions and signaling pathways, such as synaptic plasticity, memory formation, and learning. Gene expression is tissue-specific, and mutations can lead to neurodegenerative diseases, schizophrenia, etc.