N-methyl-D-aspartate-sensitive [3H]glutamate binding sites in brain synaptic membranes treated with Triton X-100.
Specific binding activity of radiolabeled L-glutamic acid, a putative central excitatory neutrotransmitter, was drastically increased with increasing concentrations of Triton X-100 used for pretreatment of rat brain synaptic membranes. The binding in these Triton-treated membranes was a protein dependent, inversely temperature-dependent, stereospecific, structure-selective and saturable process with a high affinity for the amino acid. The binding activity was invariably inhibited by agonists and antagonists for the N-methyl-D-aspartic acid (NMDA)-sensitive subclass, but not by agonists for the other subclasses of excitatory amino acid neurotransmitter receptors in the brain. Scatchard analysis revealed that the binding sites consisted of a single component with a Kd of 24.4 +/- 2.5 nM and a Bmax of 0.94 +/- 0.09 pmol/mg protein. Some endogenous tryptophan metabolites such as kynurenic acid and quinolinic acid also inhibited the binding. These results suggest that synaptic membranes may indeed contain the NMDA-sensitive receptors which are disclosed by Triton X-100 treatment.
Yoneda
Y
Y
Department of Pharmacology, Setsunan University, Hirakata, Japan.
Ogita
K
K
Ohgaki
T
T
Uchida
S
S
Meguri
H
H
D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D007700:Kinetics; D007736:Kynurenic Acid / Q000494:pharmacology; D016202:N-Methylaspartate; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000494:pharmacology*; D017378:Quinolinic Acid; D011805:Quinolinic Acids / Q000494:pharmacology; D051381:Rats; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000187:drug effects* / Q000378:metabolism; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013570:Synaptic Membranes / Q000378:metabolism*; D013696:Temperature; D014018:Tissue Distribution
D000596:Amino Acids; D005971:Glutamates; D011805:Quinolinic Acids; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter; D001224:Aspartic Acid; D018698:Glutamic Acid; D011092:Polyethylene Glycols; D016202:N-Methylaspartate; D017830:Octoxynol; D017378:Quinolinic Acid; D007736:Kynurenic Acid