PT - JOURNAL ARTICLE AU - Mary J. Clark AU - Paul J. Emmerson AU - Alfred Mansour AU - Huda Akil AU - James H. Woods AU - Philip S. Portoghese AU - Ann E. Remmers AU - Fedor Medzihradsky TI - Opioid Efficacy in a C6 Glioma Cell Line Stably Expressing the<em>Delta</em> Opioid Receptor DP - 1997 Nov 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 501--510 VI - 283 IP - 2 4099 - http://jpet.aspetjournals.org/content/283/2/501.short 4100 - http://jpet.aspetjournals.org/content/283/2/501.full SO - J Pharmacol Exp Ther1997 Nov 01; 283 AB - A C6 glioma cell line stably transfected with the ratdelta 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 anddelta-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, SNC80 and DPDPE maximally inhibited forskolin-stimulated adenylyl cyclase. These cells highly express a homogeneous population of delta opioid receptor that couple to inhibitory Go/Gi proteins. Ligand affinity for the delta opioid receptor correlates with ligand EC50 values for stimulation of [35S]GTPγS binding. The American Society for Pharmacology and Experimental Therapeutics