Distribution of D-amino-acid oxidase and D-serine in vertebrate brains

In mammalian brains, D-amino-acid oxidase activity is absent or scarce in the forebrain, is confined to the brain stem and cerebellum. and its localization is extended to the spinal cord. The oxidase-containing cells are astrocytes including Bergmann glial cells. Neither neurons, endothelial cells, oligodendrocytes nor ependymal cells show the oxidase activity. Free D-serine, a potent activator of the N-methyl-D-aspartate (NMDA) receptor, is in high levels in the forebrain (ca. 0.4 mu mol/g wet weight), and in low levels in the hindbrain. Thus, the localization of the oxidase activity is inversely correlated with the distribution of D-serine in mammalian brains. This inverse correlation is generally found in vertebrate brains. These results indicate that D-amino-acid oxidase decomposes D-amino acids including D-serine in vertebrate brains, and that the magnitude of its activity is important in determining the regional concentrations of D-amino acids in the steady states. (C) 2001 Elsevier Science B.V. All rights reserved.