Determination of delta-opioid in NG108-15 cells.

The delta-opioid receptors in mouse neuroblastoma x rat glioma NG108-15 cells were characterized by receptor binding and cAMP assays. Saturation binding assays using [3H][D-Pen5]enkephalin (DPDPE) or [3H][D-Ser2, Leu5, Thr6]enkephalin (DSLET) gave similar binding capacities (Bmax). Competition binding assays showed that DPDPE and DSLET have similar affinity for the [3H]DPDPE or 3[H]DSLET binding sites. The rank order of potency of competition with [3H]DPDPE and [3H]DSLET was similar: naltriben approximately DSLET > or = DPDPE > 7-benzylidenenaltrexone (BNTX). Both DPDPE and DSLET were found to decrease cAMP formation. The action of DSLET was antagonized by naltriben but not BNTX, while the action of DPDPE was reversed by both antagonists. Therefore, the delta-opioid receptor in NG108-15 cells has similar affinity for the agonists DPDPE and DSLET, and a higher affinity for the antagonist naltriben than BNTX.