title: Inhibitory effects of (2S, 3S)-3-[3-[4-(trifluoromethyl)benzoylamino]benzyloxy]aspartate (TFB-TBOA) on the astrocytic sodium responses to glutamate.
abstract: Astrocytes are responsible for the majority of the clearance of extracellular glutamate released during neuronal activity. dl-threo-beta-benzyloxyaspartate (TBOA) is extensively used as inhibitor of glutamate transport activity, but suffers from relatively low affinity for the transporter. Here, we characterized the effects of (2S, 3S)-3-[3-[4-(trifluoromethyl)benzoylamino]benzyloxy]aspartate (TFB-TBOA), a recently developed inhibitor of the glutamate transporter on mouse cortical astrocytes in primary culture. The glial Na(+)-glutamate transport system is very efficient and its activation by glutamate causes rapid intracellular Na(+) concentration (Na(+)(i)) changes that enable real time monitoring of transporter activity. Na(+)(i) was monitored by fluorescence microscopy in single astrocytes using the fluorescent Na(+)-sensitive probe sodium-binding benzofuran isophtalate. When applied alone, TFB-TBOA, at a concentration of 1 microM, caused small alterations of Na(+)(i). TFB-TBOA inhibited the Na(+)(i) response evoked by 200 microM glutamate in a concentration-dependent manner with IC(50) value of 43+/-9 nM, as measured on the amplitude of the Na(+)(i) response. The maximum inhibition of glutamate-evoked Na(+)(i) increase by TFB-TBOA was >80%, but was only partly reversible. The residual response persisted in the presence of the AMPA/kainate receptor antagonist CNQX. TFB-TBOA also efficiently inhibited Na(+)(i) elevations caused by the application of d-aspartate, a transporter substrate that does not activate non-NMDA ionotropic receptors. TFB-TBOA was found not to influence the membrane properties of cultured cortical neurons recorded in whole-cell patch clamp. Thus, TFB-TBOA, with its high potency and its apparent lack of neuronal effects, appears to be one of the most useful pharmacological tools available so far for studying glial glutamate transporters.
authors.affiliation: Department of Physiology, University of Lausanne, Switzerland.
authors.forename: Luigi
authors.initials: L
authors.lastname: Bozzo
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Chatton
mesh_terms: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000818:Animals; D001224:Aspartic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism*; D002478:Cells, Cultured; D002491:Central Nervous System Agents / Q000008:administration & dosage / Q000494:pharmacology*; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D026603:D-Aspartic Acid / Q000378:metabolism; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D050491:Glutamate Plasma Membrane Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D018092:Kainic Acid Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*
chemical_list: D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D001224:Aspartic Acid; D002491:Central Nervous System Agents; D026603:D-Aspartic Acid; D018691:Excitatory Amino Acid Antagonists; D050491:Glutamate Plasma Membrane Transport Proteins; D018698:Glutamic Acid; D018092:Kainic Acid Receptors; D016194:Receptors, N-Methyl-D-Aspartate; D012964:Sodium; C508240:(2S,3S)-3-(3-(4-(trifluoromethyl)benzoylamino)benzyloxy)aspartate