title: Ncm-D-aspartate: a novel caged D-aspartate suitable for activation of glutamate transporters and N-methyl-D-aspartate (NMDA) receptors in brain tissue.
abstract: The D-isomer of aspartate is both a substrate for glutamate transporters and an agonist of N-methyl-D-aspartate (NMDA) receptors. To monitor the behavior of these receptors and transporters in intact tissue we synthesized a new photo-labile analogue of D-aspartate, N-[(6-nitrocoumarin-7-yl)methyl]-D-aspartic acid (Ncm-D-aspartate). This compound was photolyzed rapidly (t(1/2)=0.11 micros) by UV light with a quantum efficiency of 0.041 at pH 7.4. In acute hippocampal slices, photolysis of Ncm-D-aspartate by brief (1 ms) exposure to UV light elicited rapidly activating inward currents in astrocytes that were sensitive to inhibition by the glutamate transporter antagonist DL-threo-beta-benzyloxyaspartic acid (TBOA). Neither Ncm-D-aspartate nor the photo-released caging group exhibited agonist or antagonist activity at glutamate transporters, and Ncm-D-aspartate did not induce transporter currents prior to photolysis. Glutamate transporter currents were also elicited in cerebellar Purkinje cells in response to photolysis of Ncm-D-aspartate. Photo-release of D-aspartate from Ncm-D-aspartate did not induce alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainate receptor or metabotropic glutamate receptor (mGluR) currents, but triggered robust NMDA receptor currents in neurons; Ncm-D-aspartate and the photolzyed caging group were similarly inert at NMDA receptors. These results indicate that Ncm-D-aspartate can be used to study NMDA receptors at excitatory synapses and interactions between transporters and receptors in brain tissue.
authors.affiliation: Department of Neuroscience, Johns Hopkins University Medical School, WBSB 813, Baltimore, MD 21205, USA.
authors.forename: Yanhua H
authors.initials: YH
authors.lastname: Huang
authors.forename: Sukumaran
authors.initials: S
authors.lastname: Muralidharan
authors.forename: Saurabh R
authors.initials: SR
authors.lastname: Sinha
authors.forename: Joseph P Y
authors.initials: JP
authors.lastname: Kao
authors.forename: Dwight E
authors.initials: DE
authors.lastname: Bergles
mesh_terms: D027322:Amino Acid Transport System X-AG / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism; D001923:Brain Chemistry / Q000187:drug effects / Q000502:physiology; D003374:Coumarins / Q000138:chemical synthesis / Q000378:metabolism; D026603:D-Aspartic Acid / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D004307:Dose-Response Relationship, Radiation; D004347:Drug Interactions; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques / Q000379:methods; D010782:Photolysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D027322:Amino Acid Transport System X-AG; D003374:Coumarins; C508334:N-((6-nitrocoumarin-7-yl)methyl)-D-aspartic acid; D016194:Receptors, N-Methyl-D-Aspartate; C120673:benzyloxyaspartate; D001224:Aspartic Acid; D026603:D-Aspartic Acid