Localization of d-serine and serine racemase in neurons and neuroglias in mouse brain

d-Serine is a novel candidate for an intrinsic ligand for the glycine site of N-methyl-d-aspartate (NMDA) receptors in mammalian brain. d-Serine and serine racemase, which produces d-serine from l-serine, have long been presumed to be localized in astrocytes. However, we have reported that d-serine immunoreactivity was observed in neurons in rats. In the present study, the distributions of d-serine and serine racemase were investigated in combination with marker proteins for neurons, astrocytes and oligodendrocytes in mice. Immunoreactivities for d-serine and serine racemase were found in neurons and oligodendrocytes. These results suggest that d-serine can be produced in neurons as well as glias and used as a neurotransmitter, which control the synaptic function of NMDA receptors.