title: Development of neuropathic pain in the rat spared nerve injury model is not prevented by a peripheral nerve block.
abstract: BACKGROUND
  The mechanisms responsible for initiation of persistent neuropathic pain after peripheral nerve injury are unclear. One hypothesis is that injury discharge and early ectopic discharges in injured nerves produce activity-dependent irreversible changes in the central nervous system. The aim of this study was to determine whether blockade of peripheral discharge by blocking nerve conduction before and 1 week after nerve injury could prevent the development and persistence of neuropathic pain-like behavior in the spared nerve injury model.
  
  
  METHODS
  Bupivacaine-loaded biodegradable microspheres embedded in fibrin glue were placed in a silicone tube around the sciatic nerve to produce a conduction block. After sensory-motor testing of block efficacy, a spared nerve injury procedure was performed. Development of neuropathic pain behavior was assessed for 4 weeks by withdrawal responses to stimulation (i.e., von Frey filaments, acetone, pinprick, radiant heat) in bupivacaine microspheres-treated animals (n = 12) and in controls (n = 11).
  
  
  RESULTS
  Bupivacaine microspheres treatment produced conduction blockade with a complete lack of sensory responsiveness in the sural territory for 6 to 10 days. Once the block wore off, the degree of hypersensitivity to stimuli was similar in both groups.
  
  
  CONCLUSIONS
  Peripheral long-term nerve blockade has no detectable effect on the development of allodynia or hyperalgesia in the spared nerve injury model. It is unlikely that injury discharge at the time of nerve damage or the early onset of ectopic discharges arising from the injury site contributes significantly to the persistence of stimulus-evoked neuropathic pain in this model.
authors.affiliation: Anesthesiology Pain Research Group, University Hospital Lausanne, Switzerland.
authors.forename: Marc R
authors.initials: MR
authors.lastname: Suter
authors.forename: Michael
authors.initials: M
authors.lastname: Papaloïzos
authors.forename: Charles B
authors.initials: CB
authors.lastname: Berde
authors.forename: Clifford J
authors.initials: CJ
authors.lastname: Woolf
authors.forename: Nicolas
authors.initials: N
authors.lastname: Gilliard
authors.forename: Donat R
authors.initials: DR
authors.lastname: Spahn
authors.forename: Isabelle
authors.initials: I
authors.lastname: Decosterd
mesh_terms: D000818:Animals; D002045:Bupivacaine / Q000494:pharmacology; D006930:Hyperalgesia / Q000628:therapy; D008297:Male; D009407:Nerve Block; D059408:Pain Management; D059348:Peripheral Nerve Injuries; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002045:Bupivacaine