L-glutamate is the major excitatory neurotransmitter in the central nervous system. The glutamate system represents an attractive molecular target in the treatment of epilepsy, neurodegenerative diseases (Alzheimer’s disease, Parkinson’s disease, Huntington’s chorea), schizophrenia, ischemia, pain, alcoholism and mood disorders[1].
Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) is an artificial glutamate analogue. Its receptor (originally named quisqualate receptor) is a non-NMDA-type ionotropic transmembrane receptor for glutamate that mediates fast synaptic transmission in the central nervous system. Like all ionotropic glutamate receptors, it consists of tetramers of four different types of subunits (GluR1-GluR4). The AMPA receptor GluA2 (GluR2) tetramer was the first and currently only glutamate receptor ion channel to be crystallized[2].
Kainate, a natural product, is an excitotoxic glutamate analogue produced by an algae, while NMDA is N-methyl-d-aspartate. Although all three glutamate receptor subtypes respond to glutamate, they can be distinguished by their response to these artificial agonists. Their distribution in the brain, physiological function, and mechanism and kinetics of activation and regulation are very different[3]. In two ways, the NMDA receptor is distinct from the other LGICs. First, it is both ligand-gated and voltage-dependent. Second, it requires co-activation by two ligands: glutamate and either d-serine or glycine. What’s more, the receptor controls a cation channel that is highly permeable to multiple monovalent ions and calcium[4].