title: Glycine taken up through GLYT1 and GLYT2 heterotransporters into glutamatergic axon terminals of mouse spinal cord elicits release of glutamate by homotransporter reversal and through anion channels.
abstract: Glycine concentration-dependently elicited [3H]D-aspartate ([3H]D-ASP) release from superfused mouse spinal cord synaptosomes. Glycine effect was insensitive to strychnine or 5,7-dichlorokynurenic acid, but was prevented by the glycine transporter blocker glycyldodecylamide. Glycine also evoked release of endogenous glutamate, which was sensitive to glycyldodecylamide and abolished in low-Na+ medium. Experiments with purified synaptosomes and gliasomes show that the glycine-evoked [3H]D-ASP release largely originates from glutamatergic nerve terminals. The glycine-evoked [3H]D-ASP release was halved by NFPS, a selective blocker of GLYT1 transporters, or by Org 25543, a selective GLYT2 blocker, and almost abolished by a mixture of the two, suggesting that activation of GLYT1 and GLYT2 present on glutamatergic terminals triggers the release of [3H]D-ASP. Accordingly, confocal microscopy experiments show localization of GLYT1 and GLYT2 in purified synaptosomes immuno-stained for the vesicular glutamate transporter vGLUT1. The glycine effect was independent of extra- and intraterminal Ca2+ ions. It was partly inhibited by the glutamate transporter blocker DL-TBOA and largely prevented by the anion channel blockers niflumic acid and NPPB. To conclude, transporters for glycine (GLYT1 or/and GLYT2) and for glutamate coexist on the same spinal cord glutamatergic terminals. Activation of glycine heterotransporters elicits glutamate release partly by homotransporter reversal and largely through anion channels.
authors.affiliation: Pharmacology and Toxicology Section, Department of Experimental Medicine, University of Genoa, Viale Cembrano 4, 16148 Genoa, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Raiteri
authors.forename: Sara
authors.initials: S
authors.lastname: Stigliani
authors.forename: Antonella
authors.initials: A
authors.lastname: Siri
authors.forename: Mario
authors.initials: M
authors.lastname: Passalacqua
authors.forename: Edon
authors.initials: E
authors.lastname: Melloni
authors.forename: Maurizio
authors.initials: M
authors.lastname: Raiteri
authors.forename: Giambattista
authors.initials: G
authors.lastname: Bonanno
mesh_terms: D026921:Amino Acid Transport Systems, Neutral / Q000378:metabolism*; D000818:Animals; D017920:Antiporters / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D005998:Glycine / Q000378:metabolism*; D050487:Glycine Plasma Membrane Transport Proteins; D051379:Mice; D017729:Presynaptic Terminals / Q000378:metabolism*; D013116:Spinal Cord / Q000378:metabolism
chemical_list: D026921:Amino Acid Transport Systems, Neutral; D017920:Antiporters; D050487:Glycine Plasma Membrane Transport Proteins; C493270:Slc6a5 protein, mouse; C493267:Slc6a9 protein, mouse; D018698:Glutamic Acid; D005998:Glycine