RELATIVE EFFICACIES OF DELTA-OPIOID RECEPTOR AGONISTS AT THE CLONED HUMAN DELTA-OPIOID RECEPTOR

The present study was conducted to determine the relative efficacies o f the selective delta-opioid receptor agonists SNC80 ((+)-4-[(alpha pe razinyl)-3-methoxybenzyl]-N,N-diethylbenzamide), pCl-DPDPE (cyclic[D-P en(2),4'-CIPhe(4), D-Pen(5)]enkephalin) and (-)-TAN67 ((-)-2-methyl-4a alpha-(3-hydroxyphenyl)-1,2,3,4,4a,5,12,12a alpha-octahydro-quinolino -[2,3,3-g]isoquinoline). Experiments compared the abilities of the thr ee drugs to competitively inhibit [H-3]naltrindole binding and also st imulate [S-35]GTP gamma S binding in membranes prepared from stably tr ansfected Chinese hamster ovary (CHO) cells that express the cloned hu man delta-opioid receptor. Efficacy was determined according to the fo rmula:efficacy=(Emax-A/E-max)(A'/A+1)x0.5. Results show that SNC80 and pCl-DPDPE had efficacy values that were about 6-7 times greater than that of(-)-TAN67.