title: Mechanisms of [(3)H]glycine release from mouse spinal cord synaptosomes selectively labeled through GLYT2 transporters.
abstract: Glycine release has been rarely studied. The aim of this work was to characterize the release of the amino acid from spinal cord glycinergic nerve endings selectively pre-labeled through glycine transporters of the GLYT2 type. Purified mouse spinal cord synaptosomes were incubated with [(3)H]glycine in the presence of the GLYT1 blocker N-[(3R)-3-([1,1'-biphenyl]-4-yloxy)-3-(4-fluorophenyl)propyl]-N-methylglycine hydrochloride and exposed in superfusion to varying concentrations of KCl, 4-aminopyridine (4-AP), or veratridine. KCl (< or = 15 micromol/L), 4-AP (up to 1 mmol/L), and veratridine (< or = 0.3 micromol/L)-provoked [(3)H]glycine release by external Ca2+-dependent, botulinum toxin C(1)-sensitive, exocytosis. The overflows evoked by higher concentrations of K+ or veratridine involved external Ca2+-independent mechanisms of different nature. Only the overflow evoked by 3 or 10 micromol/L veratridine occurred totally (3 micromol/L) or in part (10 micromol/L) by transporter reversal, being sensitive to the GLYT2 blockers 4-benzyloxy-3,5-dimethoxy-N-[1-(dimethylaminociclopentyl)-methyl] benzamide or O-[(2-benzyloxyphenyl-3-flurophenyl)methyl]-l-serine; in contrast, the external Ca2+-independent [(3)H]glycine overflow provoked by 50 mmol/L K+ was transporter-independent. This component of K+-evoked overflow and the GLYT2-independent portion of the 10 micromol/L veratridine-evoked overflow, were largely sensitive to the vesicle depletor bafilomycin or BAPTA-AM and were prevented by blocking the mitochondrial Na+/Ca2+ exchanger with 7-chloro-5-(2-chlorophenyl)-1,5-dihydro-4,1-benzothiazepin-2(3H)-one, indicating the involvement of exocytosis triggered by intraterminal mitochondrial Ca2+ ions.
authors.affiliation: Department of Experimental Medicine, Pharmacology and Toxicology Section, University of Genoa, Genoa, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Luccini
authors.forename: Luca
authors.initials: L
authors.lastname: Raiteri
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology; D005998:Glycine / Q000378:metabolism* / Q000494:pharmacology; D050487:Glycine Plasma Membrane Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors / Q000378:metabolism; D013116:Spinal Cord / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013574:Synaptosomes / Q000378:metabolism; D014316:Tritium; D014701:Veratridine / Q000494:pharmacology
chemical_list: D050487:Glycine Plasma Membrane Transport Proteins; C493270:Slc6a5 protein, mouse; D019831:Sodium-Calcium Exchanger; D014316:Tritium; D014701:Veratridine; D011188:Potassium; D002118:Calcium; D005998:Glycine