Characterization of 5,7-Dichlorokynurenate-Insensitive d-[3H]Serine Binding to Synaptosomal Fraction Isolated from Rat Brain Tissues |
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Authors: | †Masaki Matoba Urara Tomita Toru Nishikawa |
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Institution: | Department of Mental Disorder Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo;and; Department of Psychiatry, Jichi Medical School, Tochigi-ken, Japan |
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Abstract: | Abstract: 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 µ M ) of the glycine site antagonist 5,7-dichlorokynurenate (DCK). Nonspecific binding was defined in the presence of 1 m M 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 n M and a B max 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 K i values. Strychnine and 7-chlorokynurenate failed to inhibit the binding at 10 µ M . 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. |
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Keywords: | d-[3H]Serine binding 5 7-Dichlorokynurenate Strychnine-insensitive glycine binding site Synaptosomal P2 fraction Cerebellum Neutral amino acids N-Methyl-d-aspartate receptor |
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