title: Release of GABA from sensory neurons transduced with a GAD67-expressing vector occurs by non-vesicular mechanisms.
abstract: We have demonstrated that dorsal root ganglion neurons transduced with a recombinant replication-defective herpes simplex virus vector coding for glutamic acid decarboxylase (QHGAD67) release GABA to produce an analgesic effect in rodent models of pain. In this study, we examined the mechanism of transgene-mediated GABA release from dorsal root ganglion neurons in vitro and in vivo. Release of GABA from dorsal root ganglion neurons transduced with QHGAD67 was not increased by membrane depolarization induced by 60 mM extracellular K+ nor reduced by the removal of Ca2+ from the medium. Release of GABA from transduced dorsal root ganglion neurons was, however, blocked in a dose-dependent manner by NO-711, a selective inhibitor of the GABA transporter-1. The amount of GABA released from a spinal cord slice preparation, prepared from animals transduced by subcutaneous inoculation of QHGAD67 in the hind paws, was substantially increased compared to animals transduced with control vector Q0ZHG or normal animals, but the amount of GABA released was not changed by stimulation of the dorsal roots at either low (0.1 mA, 0.5-ms duration) or high (10 mA, 0.5-ms duration) intensity. We conclude that QHGAD67-mediated GABA release from dorsal root ganglion neurons is non-vesicular, independent of electrical depolarization, and that this efflux is mediated through reversal of the GABA transporter.
authors.affiliation: Department of Neurology, University of Michigan, 1500 E. Medical Center Drive, Room 1914 TC, Ann Arbor, MI 48109-0316, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Changfeng
authors.initials: C
authors.lastname: Tai
authors.forename: William C
authors.initials: WC
authors.lastname: de Groat
authors.forename: Xiang-min
authors.initials: XM
authors.lastname: Peng
authors.forename: Marina
authors.initials: M
authors.lastname: Mata
authors.forename: David J
authors.initials: DJ
authors.lastname: Fink
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004307:Dose-Response Relationship, Radiation; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D004622:Embryo, Mammalian; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018756:GABA Antagonists / Q000494:pharmacology; D005727:Ganglia, Spinal / Q000166:cytology; D005968:Glutamate Decarboxylase / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D018698:Glutamic Acid / Q000494:pharmacology; D005973:Glutamine / Q000031:analogs & derivatives / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D009475:Neurons, Afferent / Q000378:metabolism* / Q000821:virology; D009557:Nipecotic Acids / Q000494:pharmacology; D010091:Oximes / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018139:Simplexvirus / Q000235:genetics; D013127:Spinal Nerves / Q000502:physiology / Q000528:radiation effects; D014162:Transfection / Q000379:methods; D014404:Tubulin / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D007527:Isoenzymes; D009557:Nipecotic Acids; D010091:Oximes; D014404:Tubulin; D005973:Glutamine; C078793:NNC 711; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; D016291:Dizocilpine Maleate; C042626:gamma-glutamylaminomethylsulfonic acid; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1