Anti-nociception mediated by a κ opioid receptor agonist is blocked by a δ receptor agonist

A. M.W. Taylor, K. W. Roberts, A. A. Pradhan, H. A. Akbari, W. Walwyn, K. Lutfy, F. I. Carroll, C. M. Cahill, C. J. Evans

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Background and Purpose The opioid receptor family comprises four structurally homologous but functionally distinct sub-groups, the μ (MOP), δ (DOP), κ (KOP) and nociceptin (NOP) receptors. As most opioid agonists are selective but not specific, a broad spectrum of behaviours due to activation of different opioid receptors is expected. In this study, we examine whether other opioid receptor systems influenced KOP-mediated antinociception.

Experimental Approach We used a tail withdrawal assay in C57Bl/6 mice to assay the antinociceptive effect of systemically administered opioid agonists with varying selectivity at KOP receptors. Pharmacological and genetic approaches were used to analyse the interactions of the other opioid receptors in modulating KOP-mediated antinociception.

Key Results Etorphine, a potent agonist at all four opioid receptors, was not anti-nociceptive in MOP knockout (KO) mice, although etorphine is an efficacious KOP receptor agonist and specific KOP receptor agonists remain analgesic in MOP KO mice. As KOP receptor agonists are aversive, we considered KOP-mediated antinociception might be a form of stress-induced analgesia that is blocked by the anxiolytic effects of DOP receptor agonists. In support of this hypothesis, pretreatment with the DOP antagonist, naltrindole (10 mg·kg-1), unmasked etorphine (3 mg·kg-1) antinociception in MOP KO mice. Further, in wild-type mice, KOP-mediated antinociception by systemic U50,488H (10 mg·kg-1) was blocked by pretreatment with the DOP agonist SNC80 (5 mg·kg-1) and diazepam (1 mg·kg-1).

Conclusions and Implications Systemic DOP receptor agonists blocked systemic KOP antinociception, and these results identify DOP receptor agonists as potential agents for reversing stress-driven addictive and depressive behaviours mediated through KOP receptor activation.

Original languageEnglish
Pages (from-to)691-703
Number of pages13
JournalBritish Journal of Pharmacology
Volume172
Issue number2
DOIs
StatePublished - Jan 2015

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