title: P2X7 Receptor Mediates Spinal Microglia Activation of Visceral Hyperalgesia in a Rat Model of Chronic Pancreatitis.
abstract: OBJECTIVE
  Molecular mechanisms underlying the activated spinal microglia in association with the pain in chronic pancreatitis (CP) remain unknown. We tested whether P2X7R on spinal microglia mediates the pathogenesis of visceral pain using a CP rat model.
  
  
  METHODS
  The CP model was induced via intraductal injection of 2% trinitrobenzene sulfonic acid into male Sprague-Dawley rats. Hyperalgesia was assessed based on the mechanical sensitivity to Von-Frey filaments (VFFs), and nocifensive behaviors were measured in response to electrical stimulation of the pancreas. Three weeks after CP induction, spinal cord samples were harvested for immunostaining, immunoblot, and real-time polymerase chain reaction analyses of the P2X7R. Changes in nocifensive behaviors and associated molecular effectors were assessed by blocking spinal cord P2X7R pharmacologically using the selective P2X7R antagonist brilliant blue G (BBG) or genetically using short interfering RNA (siRNA).
  
  
  RESULTS
  CP induced a significant up-regulation of spinal P2X7R expression, which colocalized with a microglial marker (OX-42). Intrathecal administration of BBG significantly attenuated CP-related visceral hyperalgesia in response to VFF-mediated or electrical stimulation of the pancreas, which was associated with suppressed spinal expression of P2X7R and inhibited activation of spinal microglia. Intrathecal injection of siRNA to knock down P2X7R expression in the spinal cord would suppress the nociceptive behaviors in CP rats.
  
  
  CONCLUSIONS
  Spinal microglia P2X7R mediates central sensitization of chronic visceral pain in CP. BBG may represent an effective drug for the treatment of chronic pain in CP patients.
authors.affiliation: Institute of Brain Science School of Medicine, National Yang-Ming University, Taipei, Taiwan; Division of Gastroenterology, Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Pei-Yi
authors.initials: PY
authors.lastname: Liu
authors.affiliation: Institute of Brain Science School of Medicine, National Yang-Ming University, Taipei, Taiwan; Department of Neurology, Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: I-Hui
authors.initials: IH
authors.lastname: Lee
authors.affiliation: Department of Anesthesia and Critical Care and Department of Biomedical Engineering, E-DA Hospital/I-Shou University, Kaohsiung, Taiwan.
authors.forename: Ping-Heng
authors.initials: PH
authors.lastname: Tan
authors.affiliation: Institute of Brain Science School of Medicine, National Yang-Ming University, Taipei, Taiwan; Division of Gastroenterology, Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Yen-Po
authors.initials: YP
authors.lastname: Wang
authors.affiliation: Institute of Brain Science School of Medicine, National Yang-Ming University, Taipei, Taiwan; Department of Psychology, Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan.
authors.forename: Chia-Fen
authors.initials: CF
authors.lastname: Tsai
authors.affiliation: Division of Gastroenterology, Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Han-Chieh
authors.initials: HC
authors.lastname: Lin
authors.affiliation: Division of Gastroenterology, Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Fa-Yauh
authors.initials: FY
authors.lastname: Lee
authors.affiliation: Institute of Brain Science School of Medicine, National Yang-Ming University, Taipei, Taiwan; Division of Gastroenterology, Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan; Department of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Ching-Liang
authors.initials: CL
authors.lastname: Lu
keywords: ANOVA, analysis of variance; ATP, adenosine triphosphate sulfonic acid; BBG, brilliant blue G; Brilliant Blue G; CNS, central nervous system; CP, chronic pancreatitis; Chronic Visceral Pain; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; IT, intrathecal; P2X7R, P2X7 receptor; PBS, phosphate-buffered saline; PCR, polymerase chain reaction; Purinergic Receptors; TBS, Tris-HCl buffer solution; TNBS, trinitrobenzene sulfonic acid; VFF, von Frey filament; siRNA Knockdown; siRNA, small-interfering RNA