[3H]5,7-dichlorokynurenic acid, a novel radioligand labels NMDA receptor-associated glycine binding sites.
A strychnine-insensitive glycine binding site is located on the N-methyl-D-aspartate (NMDA)-preferring glutamate receptor complex. Kynurenic acid analogs are antagonists at this binding site. A derivative of kynurenic acid, 5,7-dichlorokynurenic acid (5,7-DCKA) was radiolabeled with 3H and used to study antagonist binding to the glycine recognition site. This ligand ( [3H]5,7-DCKA) showed high affinity (Kd = 69 nM), saturable (Bmax = 14.5 pmol/mg protein) binding to rat brain membranes. A variety of agonists and antagonists inhibited the binding of [3H]5,7-DCKA and [3H]glycine in a similar fashion (r = 0.93). In addition, glutamate site agonists and antagonists exerted opposite allosteric effects on [3H]5,7-DCKA binding suggesting that [3H]5,7-DCKA preferentially binds to the agonist-activated conformation of the receptor.
Baron
B M
BM
Merrell Dow Research Institute, Cincinnati, OH 45215.
Siegel
B W
BW
Slone
A L
AL
Harrison
B L
BL
Palfreyman
M G
MG
Hurt
S D
SD
D000494:Allosteric Regulation; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000378:metabolism; D005998:Glycine / Q000037:antagonists & inhibitors / Q000378:metabolism*; D066298:In Vitro Techniques; D007736:Kynurenic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D008024:Ligands; D008297:Male; D011073:Polyamines / Q000494:pharmacology; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013331:Strychnine / Q000494:pharmacology; D013574:Synaptosomes / Q000378:metabolism
D008024:Ligands; D011073:Polyamines; D016194:Receptors, N-Methyl-D-Aspartate; D007736:Kynurenic Acid; D013331:Strychnine; C066192:5,7-dichlorokynurenic acid; D005998:Glycine