The mammalian ionotropic glutamate receptor family encodes 18 gene products that coassemble to form ligand-gated ion channels containing an agonist recognition site, a transmembrane ion permeation pathway, and gating elements that couple agonist-induced conformational changes to the opening or closing of the permeation pore. Glutamate receptors mediate fast excitatory synaptic transmission in the central nervous system and are localized on neuronal and non-neuronal cells. These receptors regulate a broad spectrum of processes in the brain, spinal cord, retina, and peripheral nervous system. Glutamate receptors are postulated to play important roles in numerous neurological diseases and have attracted intense scrutiny. The description of glutamate receptor structure, including its transmembrane elements, reveals a complex assembly of multiple semiautonomous extracellular domains linked to a pore-forming element with striking resemblance to an inverted potassium channel. In this review we discuss International Union of Basic and Clinical Pharmacology glutamate receptor nomenclature, structure, assembly, accessory subunits, interacting proteins, gene expression and translation, post-translational modifications, agonist and antagonist pharmacology, allosteric modulation, mechanisms of gating and permeation, roles in normal physiological function, as well as the potential therapeutic use of pharmacological agents acting at glutamate receptors.

/pdf/glutamate-receptor-ion-channels-structure-regulation-and-148yts0p6h.pdf

Glutamate Receptor Ion Channels: Structure, Regulation, and Function

Excitatory amino acid transmitters

Structure and function of the brain serotonin system.

'The following abbreviations have been used in the text; I3-L-ODAP, I3-N-uxalyl-L-a,l3diaminu-prupiunic acid; ACPD, Trans-l-aminu-cydupentyl-I,3-dicarbuxylate; AMPA, a­ aminu-3-hydruxy-5-methyl-isoxazole-4-propionate; AP4, 2-amino-4-phosphonobutyrate; AP5, 2-amino-5-phuphonovalerate; ASP, aspartate; CNQX, 6-cyano-7-nitro-quinoxaline-2,3-dione; CPP, 3-(2-earboxypiperazin-4-yl)prupyl-l -phosphate; cyelo-Leu, eydo-Ieucine; DAA, D-a­ amino-adipate; DGG, y-D-glutamylglycine; DNQX, 6,7-dinitro-quinoxaline-2,3dione; EAA, excitatory amino acids; GABA, gamma-aminu-butyric acid; GDEE, glutamate diethyl ester; GLU, glutamate; GL Y, glycine; HA-966, 3-amino-l-hydroxypyrrolidone-2; lBO, ibotenate; IP, inositol phosphate; KA, kainate; KYN, kynurenate; MK-801, dibenzoeyclohepteneimine; NMDA, N-methyl-D-aspartate; PCP, phencyclidine; QA, quisqualate; SER, serine; SOP, serine­ O-phosphate; TCP, 1-[1-(2-thienyl)-eyclohexyIJpiperidine

The Excitatory Amino Acid Receptors: Their Classes, Pharmacology, and Distinct Properties in the Function of the Central Nervous System

The cellular mechanisms by which excess exposure to the excitatory neurotransmitter glutamate can produce neuronal injury are unknown. More than a decade ago it was hypothesized that glutamate neurotoxicity (GNT) is a direct consequence of excessive neuronal excitation (“excitotoxicity” hypothesis); more recently, it has been hypothesized that a Ca influx triggered by glutamate exposure might mediate GNT (Ca hypothesis). A basic test to discriminate between these hypotheses would be to determine the dependence of GNT on the extracellular ionic environment. The excitotoxicity hypothesis predicts that GNT should depend critically on the presence of extracellular Na, since that ion appears to mediate glutamate neuroexcitation in the CNS; the Ca hypothesis predicts that GNT should depend critically on the presence of extracellular Ca. The focus of the present experiments was to determine the effects of several alterations in the extracellular ionic environment upon the serial morphologic changes that occur after mouse neocortical neurons in cell culture receive toxic exposure to glutamate. The results suggest that GNT in cortical neurons can be separated into 2 components distinguishable on the basis of differences in time course and ionic dependence. The first component, marked by neuronal swelling, occurs early, is dependent on extracellular Na and Cl, can be mimicked by high K, and is thus possibly “excitotoxic.” The second component, marked by gradual neuronal disintegration, occurs late, is dependent on extracellular Ca, can be mimicked by A23187, and is thus possibly mediated by a transmembrane influx of Ca. While either component alone is ultimately capable of producing irreversible neuronal injury, the Ca-dependent mechanism predominates at lower exposures to glutamate. Glutamate exposure likely leads to a Ca influx both through glutamate-activated cation channels and through voltage- dependent Ca channels activated by membrane depolarization. Addition of 20 mM Mg, however, did not substantially block GNT; this finding, together with the observation that GNT is largely preserved in sodium- free solution, supports the notion that the activation of voltage- dependent Ca channels may not be required for lethal Ca entry. The possibility that N-methyl-D-aspartate receptors may play a dominant role in mediating glutamate-induced lethal Ca influx is discussed.

https://www.jneurosci.org/content/jneuro/7/2/369.full.pdf

Ionic dependence of glutamate neurotoxicity

2-Amino-5-phosphonovalerate (2APV), a potent and selective antagonist of amino acid-induced and synaptic excitation

CPP, a new potent and selective NMDA antagonist. Depression of central neuron responses, affinity for [3H]D-AP5 binding sites on brain membranes and anticonvulsant activity.

Substance P in the substantia nigra

The dorsal and medial raphe projections to the substantia nigra in the rat: electrophysiological, biochemical and behavioural observations.

D-α-Aminoadipate as a selective antagonist of amino acid-induced and synaptic excitation of mammalian spinal neurones

J. Davies

Papers

2-Amino-5-phosphonovalerate (2APV), a potent and selective antagonist of amino acid-induced and synaptic excitation

CPP, a new potent and selective NMDA antagonist. Depression of central neuron responses, affinity for [3H]D-AP5 binding sites on brain membranes and anticonvulsant activity.

Substance P in the substantia nigra

The dorsal and medial raphe projections to the substantia nigra in the rat: electrophysiological, biochemical and behavioural observations.

D-α-Aminoadipate as a selective antagonist of amino acid-induced and synaptic excitation of mammalian spinal neurones