title: G protein-gated inwardly rectifying potassium channel subunits 1 and 2 are down-regulated in rat dorsal root ganglion neurons and spinal cord after peripheral axotomy.
abstract: BACKGROUND
  Increased nociceptive neuronal excitability underlies chronic pain conditions. Various ion channels, including sodium, calcium and potassium channels have pivotal roles in the control of neuronal excitability. The members of the family of G protein-gated inwardly rectifying potassium (GIRK) channels, GIRK1-4, have been implicated in modulating excitability. Here, we investigated the expression and distribution of GIRK1 and GIRK2 in normal and injured dorsal root ganglia (DRGs) and spinal cord of rats.
  
  
  RESULTS
  We found that ~70% of the DRG neurons expressed GIRK1, while only <10% expressed GIRK2. The neurochemical profiles of GIRK1- and GIRK2-immunoreactive neurons were characterized using the neuronal markers calcitonin gene-related peptide, isolectin-B4 and neurofilament-200, and the calcium-binding proteins calbindin D28k, calretinin, parvalbumin and secretagogin. Both GIRK subunits were expressed in DRG neurons with nociceptive characteristics. However, while GIRK1 was widely expressed in several sensory neuronal subtypes, GIRK2 was detected mainly in a group of small C-fiber neurons. In the spinal dorsal horn, GIRK1- and -2-positive cell bodies and processes were mainly observed in lamina II, but also in superficial and deeper layers. Abundant GIRK1-, but not GIRK2-like immunoreactivity, was found in the ventral horn (laminae VI-X). Fourteen days after axotomy, GIRK1 and GIRK2 were down-regulated in DRG neurons at the mRNA and protein levels. Both after axotomy and rhizotomy there was a reduction of GIRK1- and -2-positive processes in the dorsal horn, suggesting a presynaptic localization of these potassium channels. Furthermore, nerve ligation caused accumulation of both subunits on both sides of the lesion, providing evidence for anterograde and retrograde fast axonal transport.
  
  
  CONCLUSIONS
  Our data support the hypothesis that reduced GIRK function is associated with increased neuronal excitability and causes sensory disturbances in post-injury conditions, including neuropathic pain.
authors.affiliation: School of Life Science and Technology, Harbin Institute of Technology, 150001, Harbin, China. htylv123@126.com.|Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden. htylv123@126.com.
authors.forename: Chuang
authors.initials: C
authors.lastname: Lyu
authors.affiliation: Department of Neuroscience, Science for Life Laboratory, Karolinska Institutet, 171 77, Stockholm, Sweden. Jan.Mulder@ki.se.
authors.forename: Jan
authors.initials: J
authors.lastname: Mulder
authors.affiliation: Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden. Swapnali.Barde@ki.se.
authors.forename: Swapnali
authors.initials: S
authors.lastname: Barde
authors.affiliation: Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden. Kristoffer.Sahlholm@ki.se.
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Sahlholm
authors.affiliation: Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden. Hugo.Zeberg@ki.se.
authors.forename: Hugo
authors.initials: H
authors.lastname: Zeberg
authors.affiliation: Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden. Johanna.Nilsson@ki.se.
authors.forename: Johanna
authors.initials: J
authors.lastname: Nilsson
authors.affiliation: Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden. Peter.Arhem@ki.se.
authors.forename: Peter
authors.initials: P
authors.lastname: Århem
authors.affiliation: Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden. Tomas.Hokfelt@ki.se.
authors.forename: Tomas
authors.initials: T
authors.lastname: Hökfelt
authors.affiliation: Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden. Kaj.Fried@ki.se.
authors.forename: Kaj
authors.initials: K
authors.lastname: Fried
authors.affiliation: School of Life Science and Technology, Harbin Institute of Technology, 150001, Harbin, China. tjstenshi@gmail.com.|Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden. tjstenshi@gmail.com.
authors.forename: Tie-Jun Sten
authors.initials: TJ
authors.lastname: Shi
mesh_terms: D000818:Animals; D001370:Axonal Transport; D019771:Axotomy; D015415:Biomarkers / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000235:genetics / Q000378:metabolism*; D019004:Galanin / Q000378:metabolism; D005727:Ganglia, Spinal / Q000378:metabolism*; D008159:Lumbar Vertebrae / Q000378:metabolism; D008297:Male; D009474:Neurons / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D021122:Protein Subunits / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017481:Receptors, Somatostatin / Q000378:metabolism; D013116:Spinal Cord / Q000378:metabolism*; D066148:Spinal Cord Dorsal Horn / Q000378:metabolism; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism
chemical_list: D015415:Biomarkers; D002135:Calcium-Binding Proteins; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; C497070:Kcnj6 protein, rat; D021122:Protein Subunits; D012333:RNA, Messenger; D017481:Receptors, Somatostatin; C493466:Slc17a7 protein, rat; D050598:Vesicular Glutamate Transport Protein 1; C106140:somatostatin receptor sst2A; D019004:Galanin; D052248:Nitric Oxide Synthase Type I