title: Contamination of commercially available quisqualic acid by glutamate-like and aspartate-like substances.
abstract: Six different batches of the glutamic acid analogue quisqualic acid were analyzed with high-pressure liquid chromatography (HPLC). All batches examined showed contaminant peaks. Different batches had different contaminant peaks and differing amounts of each contaminant. Every batch of quisqualic acid tested demonstrated a contaminant peak which co-eluted with exogenously added glutamic acid. Certain batches possessed a contaminant which co-eluted with aspartic acid. The levels of glutamate-like contamination ranged from 0.08 to 0.60%, and the levels of aspartate-like contamination ranged from undetectable amounts to 0.80%. The amount of combined glutamate- and aspartate-like contamination of each batch of quisqualate correlated very highly with the ability of that batch to interact with non-quisqualate receptors in an autoradiographic binding assay. These non-quisqualate receptors are likely N-methyl-D-aspartate (NMDA) receptors. Thus, when high concentrations of quisqualate are used experimentally, contamination is likely to produce spurious effects at non-quisqualate glutamate receptors. Quisqualate itself may be a more specific agonist than assumed previously.
authors.affiliation: Department of Neurology, University of Michigan Medical School, Ann Arbor 48104-1687.
authors.forename: J H
authors.initials: JH
authors.lastname: Cha
authors.forename: Z R
authors.initials: ZR
authors.lastname: Hollingsworth
authors.forename: J T
authors.initials: JT
authors.lastname: Greenamyre
authors.forename: A B
authors.initials: AB
authors.lastname: Young
mesh_terms: D001224:Aspartic Acid / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D004340:Drug Contamination; D005971:Glutamates / Q000032:analysis*; D018698:Glutamic Acid; D010069:Oxadiazoles / Q000032:analysis*; D016318:Quisqualic Acid
chemical_list: D005971:Glutamates; D010069:Oxadiazoles; D001224:Aspartic Acid; D018698:Glutamic Acid; D016318:Quisqualic Acid