title: Cellular distribution of D-serine, serine racemase and D-amino acid oxidase in the rat vestibular sensory epithelia.
abstract: Glutamate is the main neurotransmitter at the synapses between sensory cells and primary afferents in the peripheral vestibular system. Evidence has recently been obtained demonstrating that the atypical amino acid D-serine is the main endogenous co-agonist of the N-methyl-D-aspartate receptors in the CNS. We studied the distribution of D-serine and its synthesizing and degrading enzymes, serine racemase and d-amino acid oxidase in the rat vestibular sensory epithelium using immunocytochemistry. D-serine, serine racemase and D-amino acid oxidase were localized in the transitional cells, which are parasensory cells located between the sensory epithelium and the dark cells. The dark cells expressed only serine racemase. D-Serine was also detected in the supporting cells of the sensory epithelium. These cells, which are in close contact with glutamatergic synapses, express GLAST, a glial specific transporter for glutamate. They may have similar functions to glial cells in the CNS and thus expression of D-serine suggests a neuromodulator role for D-serine at the glutamatergic synapses in the peripheral vestibular system. Our data also indicate that the metabolism of D-serine is not restricted to glial cells suggesting that the amino acid may play an additional role in the peripheral nervous system.
authors.affiliation: INM, INSERM U583, Hôpital St Eloi, 34091 Montpellier Cx5, France.
authors.forename: D
authors.initials: D
authors.lastname: Dememes
authors.forename: J-P
authors.initials: JP
authors.lastname: Mothet
authors.forename: M-T
authors.initials: MT
authors.lastname: Nicolas
mesh_terms: D000818:Animals; D003605:D-Amino-Acid Oxidase / Q000378:metabolism*; D004848:Epithelium / Q000201:enzymology / Q000378:metabolism; D027341:Excitatory Amino Acid Transporter 1 / Q000378:metabolism; D018698:Glutamic Acid / Q000502:physiology; D007150:Immunohistochemistry; D008297:Male; D018613:Microscopy, Confocal; D018377:Neurotransmitter Agents / Q000378:metabolism; D015388:Organelles / Q000378:metabolism; D019998:Racemases and Epimerases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012694:Serine / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism; D014722:Vestibule, Labyrinth / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure*; D000099300:Serine Racemase
chemical_list: D003605:D-Amino-Acid Oxidase; D027341:Excitatory Amino Acid Transporter 1; D018698:Glutamic Acid; D018377:Neurotransmitter Agents; D019998:Racemases and Epimerases; D012694:Serine; D000099300:Serine Racemase; C493392:Slc1a3 protein, rat