Excitatory neurotransmitters in the central nervous system, the amino acids l-glutamate and l-aspartate, that may be involved in long-term potentiation, and that 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 widely distributed through the central nervous system, particularly in the telencephalon; N- and Q-type receptors tend to occur together, and their distribution is complementary to that of 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. The N-type receptor shows voltage-gated ion channel properties, leading to a regenerative response, and this may be important for long-term potentiation. Invertebrate glutamate receptors differ significantly from those of vertebrates. There are also inhibitory amino acids: γ-aminobutyric acid (GABA) and glycine are fast inhibitory transmitters in the central nervous system, their effects being blocked by bicuculline and strychnine respectively.
Subjects: Medicine and Health — Chemistry.