Opioid efficacy in a C6 glioma cell line stably expressing the delta opioid receptor

Mary J. Clark, Paul J. Emmerson, Alfred Mansour, Huda Akil, James H. Woods, Philip S. Portoghese, Ann E. Remmers, Fedor Medzihradsky

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

Abstract

A C6 glioma cell line stably transfected with the rat delta opioid receptor (C6δ) was used to characterize receptor binding and G protein activation by both peptide and nonpeptide delta opioid ligands. The ligand binding affinities for [3H]naltrindole and [3H]pCl-[D-Pen2,D- Pen5]enkephalin (DPDPE) were similar to those observed in monkey brain membranes. The nonpeptide agonists, BW373U86 and SNC80, as well as peptide agonist [D-Ser2,L-Leu5]enkephalyl-Thr maximally stimulated [35S]GTPγS binding by 640, 654 and 576%, respectively, over basal. The peptide agonists, DPDPE and deltorphin II, both stimulated [35S]GTPγS binding by 375%. Etorphine, diprenorphine, oxymorphindole and 7-spiroindanyloxymorphone were also partial agonists in this assay, although they were less efficacious than deltorphin II. Stimulation of [35S]GTPγS binding by agonists was blocked completely by pertussis toxin pretreatment. Both delta-1 and delta-2 selective antagonists 7-benzylidenenaltrexone and a benzofuran analog of naltrindole displayed high affinity for the cloned receptor (0.04 and 0.08 nM) and antagonized the stimulation of [35S]GTPγS binding by BW373U86 and DPDPE with similar potencies. Other evidence suggesting the lack of receptor subtypes includes the finding that stimulation of [35S]GTPγS binding by receptor subtype selective ligands DPDPE and deltorphin II was not additive. BW373U86, SNC8O and DPDPE maximally inhibited forskolin-stimulated adenylyl cyclase. These cells highly express a homogeneous population of delta opioid receptor that couple to inhibitory G(o)/G(i) proteins. Ligand affinity for the delta opioid receptor correlates with ligand EC50 values for stimulation of [35S]GTPγS binding.

Original languageEnglish (US)
Pages (from-to)501-510
Number of pages10
JournalJournal of Pharmacology and Experimental Therapeutics
Volume283
Issue number2
StatePublished - Nov 1997
Externally publishedYes

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology

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