title: Glutamic acid-insensitive [3H]kainic acid binding in goldfish brain.
abstract: Kainic acid is supposed to be a specific agonist for a subclass of excitatory glutamate receptors in the vertebrate CNS. An investigation of (2 nM) [3H]kainic acid binding sites in goldfish brain, using quantitative autoradiography, has revealed evidence for two types of kainic acid receptors which differ in sensitivity to glutamic acid. L-Glutamic acid (0.1-1 mM) displaced over 95% of specific [3H]kainic acid binding elsewhere in the brain but only 10-50% in the cerebellum and cerebellar crest. These structures apparently contain [3H]kainic acid binding sites that are extremely insensitive to glutamic acid. The glutamic acid-insensitive [3H]kainic acid binding was not displaced by quisqualic acid, kynurenic acid, alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid (AMPA), or N-methyl-D-aspartatic acid, but was completely displaced by the kainic acid analogue domoic acid. The data indicate that two types of high affinity binding sites for [3H]kainic acid exist in the goldfish brain: glutamic acid-sensitive and glutamic acid-insensitive. High affinity [3H]kainic acid binding may therefore not always represent binding to subsets of glutamic acid receptors.
authors.affiliation: Mental Health Research Institute, University of Michigan, Ann Arbor 48104-1687.
authors.forename: R E
authors.initials: RE
authors.lastname: Davis
authors.forename: G R
authors.initials: GR
authors.lastname: Wilmot
authors.forename: J H
authors.initials: JH
authors.lastname: Cha
mesh_terms: D000818:Animals; D001345:Autoradiography; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D006054:Goldfish; D007051:Ibotenic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D007608:Kainic Acid / Q000031:analogs & derivatives / Q000378:metabolism*; D008024:Ligands; D009498:Neurotoxins / Q000378:metabolism; D014018:Tissue Distribution; D014316:Tritium; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
chemical_list: D005971:Glutamates; D008024:Ligands; D009498:Neurotoxins; D014316:Tritium; D007051:Ibotenic Acid; D018698:Glutamic Acid; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; C012301:domoic acid; D007608:Kainic Acid