title: Extracellular concentration of endogenous free D-serine in the rat brain as revealed by in vivo microdialysis.
abstract: Using an in vivo microdialysis technique, we have measured the extracellular concentration of endogenous free D-serine in comparison with that of L-serine, glycine and L-glutamate in the discrete brain areas of the freely moving rat. A high concentration of D-serine was observed in the dialysate obtained from the medial prefrontal cortex and striatum, whereas the cerebellar dialysate contained only a trace amount of the D-amino acid. The regional variation in the basal overflow of D-serine was proportional to that of its tissue levels which has been shown to closely correlate with the distribution of the N-methyl-D-aspartate type excitatory amino acid receptor. In contrast, the extracellular release of glycine and L-glutamate was higher in the cerebellum and very low in the striatum. The extracellular concentrations of L-serine were more than three times those of striatal D-serine in the three regions. Neither addition of a sodium channel blocker, tetrodotoxin (2 microM), nor deprivation of Ca2+ from the perfusate reduced the basal extracellular levels of the four amino acids tested in the medial prefrontal cortex. Furthermore, intra-frontal cortex perfusion of a sodium channel activator, veratrine (200 micrograms/ml), caused an increase in the extracellular release of glycine and L-glutamate but a slight decrease in that of D-serine in a tetrodotoxin-sensitive manner in the cortical region.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Precursory Research for Embryonic Science and Technology (PRESTO), Research Development Corporation of Japan, Saitama.
authors.forename: A
authors.initials: A
authors.lastname: Hashimoto
authors.forename: T
authors.initials: T
authors.lastname: Oka
authors.forename: T
authors.initials: T
authors.lastname: Nishikawa
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002531:Cerebellum / Q000378:metabolism; D003342:Corpus Striatum / Q000378:metabolism; D005110:Extracellular Space / Q000737:chemistry / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D005998:Glycine / Q000378:metabolism; D007700:Kinetics; D008297:Male; D017551:Microdialysis / Q000379:methods; D009928:Organ Specificity; D017397:Prefrontal Cortex / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012694:Serine / Q000032:analysis / Q000378:metabolism*; D026941:Sodium Channel Blockers; D013237:Stereoisomerism; D013779:Tetrodotoxin / Q000494:pharmacology; D014702:Veratrine / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D026941:Sodium Channel Blockers; D018698:Glutamic Acid; D013779:Tetrodotoxin; D012694:Serine; D014702:Veratrine; D005998:Glycine