FUNCTIONAL EXPRESSION, ACTIVATION AND DESENSITIZATION OF OPIOID RECEPTOR-LIKE RECEPTOR ORL(1) IN NEUROBLASTOMA X GLIOMA NG108-15 HYBRID-CELLS

Neuroblastoma X glioma NG108-15 hybrid cells have been examined for th e expression of opioid receptor-like receptor (ORL(1)). [H-3]Nocicepti n/orphanin FQ (OFQ) bound to the cell membrane specifically (K-d=3.6+/ -0.6 nM) and inhibited forskolin-stimulated cAMP accumulation (EC(50) = 0.72+/-0.3 nM), The responsiveness of NG108-15 cells to nociceptin/O FQ was blocked by pertussis toxin but not by naltrindole. The inhibito ry activity of nociceptin/OFQ was significantly reduced after a precha llenge with the same peptide but was not influenced by DPDPE pretreatm ent, indicating acute and homologous desensitization of ORL(1) recepto rs. Naltrindole caused the overshoot of cAMP in DPDPE-pretreated cells but not in nociceptin/OFQ-pretreated cells, The results indicate that ORL(1) is functionally expressed and does not cross-interact with spe cific ligands of the delta opioid receptor in NG108-15 cells. (C) 1997 Federation of European Biochemical Societies.