title: Early Postoperative Nociceptive Threshold and Production of Brain-Derived Neurotrophic Factor Induced by Plantar Incision Are Not Influenced with Minocycline in a Rat: Role of Spinal Microglia.
abstract: BACKGROUND
  Brain-derived neurotrophic factor (BDNF) from spinal microglia is crucial for aberrant nociceptive signaling in several pathological pain conditions, including postoperative pain. We assess the contribution of spinal microglial activation and associated BDNF overexpression to the early post-incisional nociceptive threshold.
  
  
  METHODS
  Male Sprague-Dawley rats were implanted with an intrathecal catheter. A postoperative pain model was established by plantar incision. Thermal and mechanical nociceptive responses were assessed by infrared radiant heat and von Frey filaments before and after plantar incision. Rats were injected intrathecally the microglial activation inhibitor minocycline before incision, 24 h after incision, or both. Other groups were subjected to the same treatments and the L4-L5 spinal cord segment removed for immunohistochemical analysis of microglia activation and BNDF expression.
  
  
  RESULTS
  Plantar incision reduced both thermal latency and mechanical threshold, indicating thermal hypersensitivity and mechanical allodynia. Minocycline temporally reduced thermal withdrawal latency but had no effect on mechanical withdrawal threshold, spinal microglial activity, or dorsal horn BDNF overexpression during the early post-incision period.
  
  
  CONCLUSIONS
  These results suggest that spinal microglia does not contribute substantially to post-incisional nociceptive threshold. The BDNF overexpression response that may contribute to postoperative hyperalgesia and allodynia is likely derived from other sources.
authors.affiliation: Division of Dento-oral Anesthesiology, Tohoku University Graduate School of Dentistry, Sendai, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Masaki
authors.forename: Kentaro
authors.initials: K
authors.lastname: Mizuta
authors.forename: Norimasa
authors.initials: N
authors.lastname: Ohtani
authors.forename: Kanta
authors.initials: K
authors.lastname: Kido
keywords: Brain-derived neurotrophic factor; Early postoperative pain; Microglia; Spinal cord