Characterization of 5,7-dichlorokynurenate-insensitive D-[3H]serine binding to synaptosomal fraction isolated from rat brain tissues.
To explore target sites for endogenous D-serine that are different from the glycine site of the N-methyl-D-aspartate (NMDA) type glutamate receptor, we have studied the binding of D-[3H]serine to the synaptosomal P2 fraction prepared from the rat brain and peripheral tissues in the presence of an excess concentration (100 microM) of the glycine site antagonist 5,7-dichlorokynurenate (DCK). Nonspecific binding was defined in the presence of 1 mM unlabeled D-serine. Association, dissociation, and saturation experiments indicated that D-[3H]serine bound rapidly and reversibly to a single population of recognition sites in the cerebellar P2 fraction in the presence of DCK, with a K(D) of 614 nM and a Bmax of 2.07 pmol/mg of protein. D-Serine, L-serine, and glycine produced a total inhibition of the specific DCK-insensitive D-[3H]serine binding to the cerebellum with similar Ki values. Strychnine and 7-chlorokynurenate failed to inhibit the binding at 10 microM. The profiles of displacement of the DCK-insensitive D-[3H]serine binding by various amino acids and glutamate and glycine receptor-related compounds differ from those of any other defined recognition sites. DCK-insensitive D-[3H]serine binding was at high levels in the cerebral cortex and cerebellum but very low in the kidney and liver. The present findings indicate that the DCK-insensitive D-[3H]serine binding site could be a novel candidate for a target for endogenous D-serine in mammalian brains.
Matoba
M
M
Department of Mental Disorder Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan.
Tomita
U
U
Nishikawa
T
T
D000818:Animals; D001665:Binding Sites / Q000502:physiology; D001667:Binding, Competitive / Q000502:physiology; D001923:Brain Chemistry / Q000502:physiology*; D002412:Cations / Q000494:pharmacology; D002531:Cerebellum / Q000737:chemistry / Q000378:metabolism; D002540:Cerebral Cortex / Q000737:chemistry / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D005998:Glycine / Q000037:antagonists & inhibitors; D007668:Kidney / Q000737:chemistry / Q000378:metabolism; D007736:Kynurenic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D008297:Male; D017830:Octoxynol / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012694:Serine / Q000378:metabolism / Q000494:pharmacology*; D013347:Subcellular Fractions / Q000737:chemistry / Q000378:metabolism; D013574:Synaptosomes / Q000737:chemistry / Q000378:metabolism*; D014316:Tritium
D002412:Cations; D003902:Detergents; D018691:Excitatory Amino Acid Antagonists; D014316:Tritium; D012694:Serine; D017830:Octoxynol; D007736:Kynurenic Acid; C066192:5,7-dichlorokynurenic acid; D005998:Glycine