title: Effect of antioxidant treatment on spinal GABA neurons in a neuropathic pain model in the mouse.
abstract: One feature of neuropathic pain is a reduced spinal gamma-aminobutyric acid (GABA)-ergic inhibitory function. However, the mechanisms behind this attenuation remain to be elucidated. This study investigated the involvement of reactive oxygen species in the spinal GABA neuron loss and reduced GABA neuron excitability in spinal nerve ligation (SNL) model of neuropathic pain in mice. The importance of spinal GABAergic inhibition in neuropathic pain was tested by examining the effects of intrathecally administered GABA receptor agonists and antagonists in SNL and naïve mice, respectively. The effects of SNL and antioxidant treatment on GABA neuron loss and functional changes were examined in transgenic GAD67-enhanced green fluorescent protein positive (EGFP+) mice. GABA receptor agonists transiently reversed mechanical hypersensitivity of the hind paw in SNL mice. On the other hand, GABA receptor antagonists made naïve mice mechanically hypersensitive. Stereological analysis showed that the numbers of enhanced green fluorescent protein positive (EGFP+) GABA neurons were significantly decreased in the lateral superficial laminae (I-II) on the ipsilateral L5 spinal cord after SNL. Repeated antioxidant treatments significantly reduced the pain behaviors and prevented the reduction in EGFP+ GABA neurons. The response rate of the tonic firing GABA neurons recorded from SNL mice increased with antioxidant treatment, whereas no change was seen in those recorded from naïve mice, which suggested that oxidative stress impaired some spinal GABA neuron activity in the neuropathic pain condition. Together the data suggest that neuropathic pain, at least partially, is attributed to oxidative stress, which induces both a GABA neuron loss and dysfunction of surviving GABA neurons.
authors.affiliation: Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX, USA.
authors.forename: June
authors.initials: J
authors.lastname: Yowtak
authors.forename: Jigong
authors.initials: J
authors.lastname: Wang
authors.forename: Hee Young
authors.initials: HY
authors.lastname: Kim
authors.forename: Ying
authors.initials: Y
authors.lastname: Lu
authors.forename: Kyungsoon
authors.initials: K
authors.lastname: Chung
authors.forename: Jin Mo
authors.initials: JM
authors.lastname: Chung
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001522:Behavior, Animal; D002452:Cell Count; D003497:Cyclic N-Oxides / Q000494:pharmacology / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D016166:Free Radical Scavengers / Q000494:pharmacology; D018755:GABA Agonists / Q000627:therapeutic use; D018756:GABA Antagonists / Q000627:therapeutic use; D049452:Green Fluorescent Proteins; D006930:Hyperalgesia / Q000188:drug therapy / Q000523:psychology; D008026:Ligation; D051379:Mice; D008822:Mice, Transgenic; D009437:Neuralgia / Q000188:drug therapy*; D009474:Neurons / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D010812:Physical Stimulation; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects*; D013127:Spinal Nerves / Q000293:injuries; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D000975:Antioxidants; D003497:Cyclic N-Oxides; D016166:Free Radical Scavengers; D018755:GABA Agonists; D018756:GABA Antagonists; D049452:Green Fluorescent Proteins; C029217:phenyl-N-tert-butylnitrone; D005680:gamma-Aminobutyric Acid
keywords: Free radicals; GABA; Neuropathic pain; Reactive oxygen species; Spinal cord dorsal horn neurons