excitatory amino acid

The naturally occurring amino acids L-glutamate and L-aspartate and their synthetic analogues, notably kainate, quisqualate, and NMDA. They have the properties of excitatory neurotransmitters in the CNS, may be involved in long-term potentiation, and can act as excitotoxins. At least three classes of EAA receptor have been identified; the agonists of the N-type receptor are L-aspartate, NMDA, and ibotenate; the agonists of the Q-type receptor are L-glutamate and quisqualate; agonists of the K-type are L-glutamate and kainate. All three receptor types are found widely in the CNS, and particularly the telencephalon; N- and Q-type receptors tend to occur together, and may interact; their distribution is complementary to the K-type receptors. The ion fluxes through the Q and K receptors are relatively brief, whereas the flux through the N-type is longer, and carries a significant amount of calcium. Additionally the N-type receptor is blockaded by magnesium near the resting potential, and thus shows voltage-gated ion channel properties, leading to a regenerative response; this is why N-type receptors have been linked to long-term potentiation. Invertebrate glutamate receptors may not have the same properties as those described above.