title: Blocking the P2X7 receptor improves outcomes after axonal fusion.
abstract: BACKGROUND
  Activation of the P2X7 receptor on peripheral neurons causes the formation of pannexin pores, which allows the influx of calcium across the cell membrane. Polyethylene glycol (PEG) and methylene blue have previously been shown to delay Wallerian degeneration if applied during microsuture repair of the severed nerve. Our hypothesis is that by modulating calcium influx via the P2X7 receptor pathway, we could improve PEG-based axonal repair. The P2X7 receptor can be stimulated or inhibited using bz adenosine triphosphate (bzATP) or brilliant blue (FCF), respectively.
  
  
  METHODS
  A single incision rat sciatic nerve injury model was used. The defect was repaired using a previously described PEG methylene blue fusion protocol. Experimental animals were treated with 100 μL of 100 μM FCF solution (n = 8) or 100 μL of a 30 μM bzATP solution (n = 6). Control animals received no FCF, bzATP, or PEG. Compound action potentials were recorded prior to transection (baseline), immediately after repair, and 21 d postoperatively. Animals underwent behavioral testing 3, 7, 14, and 21 d postoperatively. After sacrifice, nerves were fixed, sectioned, and immunostained to allow for counting of total axons.
  
  
  RESULTS
  Rats treated with FCF showed an improvement compared with control at all time points (n = 8) (P = 0.047, 0.044, 0.014, and 0.0059, respectively). A statistical difference was also shown between FCF and bzATP at d 7 (P < 0.05), but not shown with d 3, 14, and 21 (P > 0.05).
  
  
  CONCLUSIONS
  Blocking the P2X7 receptor improves functional outcomes after PEG-mediated axonal fusion.
authors.affiliation: Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA. charlie.feo@vanderbilt.edu
authors.forename: Charles L
authors.initials: CL
authors.lastname: Rodriguez-Feo
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Sexton
authors.forename: Richard B
authors.initials: RB
authors.lastname: Boyer
authors.forename: Alonda C
authors.initials: AC
authors.lastname: Pollins
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Cardwell
authors.forename: Lillian B
authors.initials: LB
authors.lastname: Nanney
authors.forename: R Bruce
authors.initials: RB
authors.lastname: Shack
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Mikesh
authors.forename: Christopher H
authors.initials: CH
authors.lastname: McGill
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Driscoll
authors.forename: George D
authors.initials: GD
authors.lastname: Bittner
authors.forename: Wesley P
authors.initials: WP
authors.lastname: Thayer
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology; D001557:Benzenesulfonates / Q000494:pharmacology; D004396:Coloring Agents / Q000494:pharmacology; D004337:Drug Carriers / Q000494:pharmacology; D008297:Male; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009416:Nerve Regeneration / Q000187:drug effects / Q000502:physiology; D019635:Neurosurgical Procedures; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D011092:Polyethylene Glycols / Q000494:pharmacology; D058920:Purinergic P2X Receptor Antagonists / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D058486:Receptors, Purinergic P2X7 / Q000502:physiology*; D020426:Sciatic Neuropathy / Q000188:drug therapy* / Q000503:physiopathology*; D014855:Wallerian Degeneration / Q000188:drug therapy / Q000503:physiopathology; D014945:Wound Healing / Q000187:drug effects / Q000502:physiology
chemical_list: D001557:Benzenesulfonates; D004396:Coloring Agents; D004337:Drug Carriers; D010975:Platelet Aggregation Inhibitors; D058920:Purinergic P2X Receptor Antagonists; D058486:Receptors, Purinergic P2X7; D011092:Polyethylene Glycols; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; D000255:Adenosine Triphosphate; C006796:brilliant blue
keywords: 2′,3′-O-(benzoyl-4-benzoyl)-ATP; Brilliant blue FCF; Hydrophilic polymers; Methylene blue; P2x7 receptor; Polyethylene glycol; Single-incision axonal repair; Traumatic neuropathy