Roles of opioid receptor subtype in the spinal antinociception of selective cyclooxygenase 2 inhibitor

• Published in: The Korean journal of pain Vol. 23; no. 4; pp. 236 - 241
• Main Authors: Choi, Cheol Hun, Kim, Woong Mo, Lee, Hyung Gon, Jeong, Cheol Won, Kim, Chang Mo, Lee, Seong Heon, Yoon, Myung Ha
• Format: Journal Article
• Language: English
• Published: Korea (South) The Korean Pain Society 01.12.2010; 대한통증학회
• Subjects: Original; 마취과학; intrathecal; cyclooxygenase; antinociception; opioid receptor subtype
• ISSN: 2005-9159; 2093-0569
• DOI: 10.3344/kjp.2010.23.4.236

Selective inhibitors of cyclooxygenase (COX)-2 are commonly used analgesics in various pain conditions. Although their actions are largely thought to be mediated by the blockade of prostaglandin (PG) biosynthesis, evidences suggesting endogenous opioid peptide link in spinal antinociception of COX inhibitor have been reported. We investigated the roles of opioid receptor subtypes in the spinal antinociception of selective COX-2 inhibitor. To examine the antinociception of a selective COX-2 inhibitor, DUP-697 was delivered through an intrathecal catheter, 10 minutes before the formalin test in male Sprague-Dawley rats. Then, the effect of intrathecal pretreatment with CTOP, naltrindole and GNTI, which are µ, δ and κ opioid receptor antagonist, respectively, on the analgesia induced by DUP-697 was assessed. Intrathecal DUP-697 reduced the flinching response evoked by formalin injection during phase 1 and 2. Naltrindole and GNTI attenuated the antinociceptive effect of intrathecal DUP-697 during both phases of the formalin test. CTOP reversed the antinociception of DUP-697 during phase 2, but not during phase 1. Intrathecal DUP-697, a selective COX-2 inhibitor, effectively relieved inflammatory pain in rats. The δ and κ opioid receptors are involved in the activity of COX-2 inhibitor on the facilitated state as well as acute pain at the spinal level, whereas the µ opioid receptor is related only to facilitated pain.