Yonsei Med J.  2014 Nov;55(6):1631-1639. 10.3349/ymj.2014.55.6.1631.

Epidural Dexamethasone Decreased Inflammatory Hyperalgesia and Spinal cPLA2 Expression in a Rat Formalin Test

Affiliations
  • 1Department of Anesthesiology and Pain Medicine, Korea University College of Medicine, Seoul, Korea. anejhkim@korea.ac.kr

Abstract

PURPOSE
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.
MATERIALS AND 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 microg of epidural dexamethasone group decreased as compared to control, 30 microg of epidural dexamethasone, 100 microg of epidural dexamethasone, and 300 microg of systemic dexamethasone groups. The expression of cPLA2 decreased in Rexed laminae I-II in 300 microg of the epidural dexamethasone group compared with the ones in the control group.
CONCLUSION
Taken together, these results suggest that 300 microg 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.

Keyword

Cytosolic phospholipase A2; dexamethasone; epidural injections; formalin test

MeSH Terms

Animals
Anti-Inflammatory Agents/*pharmacology
Dexamethasone/*pharmacology
Formaldehyde/*adverse effects
Group IV Phospholipases A2/*metabolism
Hyperalgesia/*drug therapy
Injections, Epidural
Male
Pain/chemically induced/*metabolism
Pain Measurement
Rats
Rats, Sprague-Dawley
Spinal Cord/*metabolism
Anti-Inflammatory Agents
Dexamethasone
Formaldehyde
Group IV Phospholipases A2
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