title: The pharmacological stimulation of NMDA receptors via co-agonist site: an fMRI study in the rat brain.
abstract: d-Serine has been proposed as an endogenous modulator at the co-agonist glycine-binding site of N-methyl-d-aspartate (NMDA) receptors. There is still some debate as to whether this site is saturated in vivo, but it seems likely that this depends on regional differences in local glycine or d-serine concentrations. In order to identify areas where the co-agonist site was not fully activated in vivo, we studied the effect of intraperitoneal d-serine administration in the rat brain using functional magnetic resonance imaging (fMRI). Using contrast agent injection, the variations in the relative cerebral blood volume (CBVrel) in several regions of interest were evaluated. d-Serine (50 mg/kg) elicited a significant statistical increase in the CBVrel in the hippocampus. This effect was inhibited by the specific full antagonist of the co-agonist glycine site L-701,324 indicating that the hippocampal activation occurred through the binding of the agonist d-serine to the glycine-binding site of NMDA receptors. This result demonstrates that in the hippocampus, the co-agonist sites of NMDA receptors are not endogenously saturated under our experimental conditions, suggesting an important role of d-serine in the modulation of receptor function in the hippocampus.
authors.affiliation: Departamento de Anatomia, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Av. Pau Brasil s/n, 21940-900 Rio de Janeiro, RJ, Brazil. rogerio@anato.ufrj.br
authors.forename: Rogério
authors.initials: R
authors.lastname: Panizzutti
authors.forename: Martin
authors.initials: M
authors.lastname: Rausch
authors.forename: Stefan
authors.initials: S
authors.lastname: Zurbrügg
authors.forename: Diana
authors.initials: D
authors.lastname: Baumann
authors.forename: Nicolau
authors.initials: N
authors.lastname: Beckmann
authors.forename: Markus
authors.initials: M
authors.lastname: Rudin
mesh_terms: D000818:Animals; D001921:Brain / Q000098:blood supply / Q000187:drug effects*; D001931:Brain Mapping; D004347:Drug Interactions; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010100:Oxygen / Q000097:blood; D015363:Quinolones / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism*; D012694:Serine / Q000494:pharmacology
chemical_list: D018691:Excitatory Amino Acid Antagonists; D015363:Quinolones; D016194:Receptors, N-Methyl-D-Aspartate; D012694:Serine; C094635:L 701324; D010100:Oxygen