Functional expression, activation and desensitization of opioid receptorlike receptor ORL(1) in neuroblastoma x glioma NG108-15 hybrid cells

Neuroblastoma X glioma NG108-15 hybrid cells have been examined for the expression of opioid receptor-like receptor (ORL(1)). [H-3]Nociceptin/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/OFQ was blocked by pertussis toxin but not by naltrindole. The inhibitory activity of nociceptin/OFQ was significantly reduced after a prechallenge with the same peptide but was not influenced by DPDPE pretreatment, indicating acute and homologous desensitization of ORL(1) receptors. 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 specific ligands of the delta opioid receptor in NG108-15 cells. (C) 1997 Federation of European Biochemical Societies.