title: Epidural dexamethasone decreased inflammatory hyperalgesia and spinal cPLA₂ expression in a rat formalin test.
abstract: OBJECTIVE
  The aim of this study was to investigate the effect of epidural dexamethasone on analgesia and cytosolic phospholipase A₂ (cPLA₂) expression in the spinal cord in a rat formalin test.
  
  
  METHODS
  Epidural dexamethasone injection was performed to Sprague-Dawley rats with a 25 gauge needle under fluoroscopy. Following the epidural injection, a formalin induced pain behavior test was performed. Next, the spinal cords corresponding to L4 dorsal root ganglion was extracted to observe the cPLA₂ expression.
  
  
  RESULTS
  There were no differences in pain response during phase I among the groups. The phase II pain response in 300 μg of epidural dexamethasone group decreased as compared to control, 30 μg of epidural dexamethasone, 100 μg of epidural dexamethasone, and 300 μg of systemic dexamethasone groups. The expression of cPLA₂ decreased in Rexed laminae I-II in 300 μg of the epidural dexamethasone group compared with the ones in the control group.
  
  
  CONCLUSIONS
  Taken together, these results suggest that 300 μg of epidural dexamethasone has an attenuating effect on the peripheral inflammatory tissue injury induced hyperalgesia and this effect is mediated through the inhibition of intraspinal cPLA₂ expression and the primary site of action is the laminae I-II of the spinal cord.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Sam-Hong
authors.initials: SH
authors.lastname: Min
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Jung-Sub
authors.initials: JS
authors.lastname: Soh
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Ji-Yong
authors.initials: JY
authors.lastname: Park
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Sung-Uk
authors.initials: SU
authors.lastname: Choi
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Hye-Won
authors.initials: HW
authors.lastname: Lee
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University College of Medicine, Seoul, Korea.
authors.forename: Jae-Jin
authors.initials: JJ
authors.lastname: Lee
authors.affiliation: Department of Anesthesiology and Pain Medicine, Korea University College of Medicine, Seoul, Korea. anejhkim@korea.ac.kr.
authors.forename: Jae-Hwan
authors.initials: JH
authors.lastname: Kim
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D003907:Dexamethasone / Q000494:pharmacology*; D005557:Formaldehyde / Q000009:adverse effects*; D054513:Group IV Phospholipases A2 / Q000378:metabolism*; D006930:Hyperalgesia / Q000188:drug therapy*; D007268:Injections, Epidural; D008297:Male; D010146:Pain / Q000139:chemically induced / Q000378:metabolism*; D010147:Pain Measurement; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000378:metabolism*
chemical_list: D000893:Anti-Inflammatory Agents; D005557:Formaldehyde; D003907:Dexamethasone; D054513:Group IV Phospholipases A2
keywords: Cytosolic phospholipase A₂; dexamethasone; epidural injections; formalin test