Etonitazene-induced antinociception in μ1 opioid receptor deficient CXBK mice: Evidence for a role for μ2 receptors in supraspinal antinociception

Charlene D. Connelly, Rebecca P. Martinez, James J. Schupsky, Frank Porreca, Robert B. Raffa

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


The prevailing view is that supraspinal μ opioid-mediated antinociception in mice is mediated via the μ1 subtype. The purpose of the present study was to determine if the highly μ-selective compound etonitazene could produce supraspinal (intracerebroventricular; i.c.v.) antinociception in CXBK mice, which are deficient in brain μ1, but not μ2, opioid receptors. CXBK or normal Crl:CD-1 ®(ICR)BR mice were administered graded doses of etonitazene i.c.v. and 15 min later antinociception was assessed by a standard radiant-heat or 55°C water tail-flick test. Etonitazene produced dose-related antinociception that was blocked by naloxone and by β-FNA (demonstrating a μ opioid mechanism), but not by either ICI-174,864 or naltrindole (demonstrating the lack of involvement of δ opioid receptors). These findings suggest that μ2 opioid receptors are important contributors to opioid-induced supraspinal antinociception in mice.

Original languageEnglish (US)
Pages (from-to)PL369-PL374
JournalLife Sciences
Issue number21
StatePublished - 1994


  • CXBK mice
  • analgesia
  • antinociception
  • opioid receptor subtypes
  • opioid μ receptors
  • μ/μ subtypes

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Pharmacology, Toxicology and Pharmaceutics(all)


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