Nociceptin receptor-mediated Ca2+ channel inhibition and its desensitization in NG108-15 cells.

It has been shown that the membrane of hybrid NG108-15 neuroblastoma x glioma cells contains a high-affinity binding site for nociceptin. In the present study, we first demonstrated the expression of nociceptin receptor mRNA in NG108-15 cells. Application of nociceptin to NG108-15 cells produced a concentration-dependent (EC50 = 29 nM) inhibition of Ca2+ channel currents in a pertussis toxin-sensitive fashion. This nociceptin-induced inhibition of Ca2+ channel currents was prevented in the presence of omega-conotoxin GVIA, a blocker of the N-type Ca2+ channel, and had both voltage-dependent and -independent components. Prolonged application of nociceptin elicited homologous desensitization of the inhibition with a time constant of 5.3 min. These results indicate that the nociceptin receptor is coupled to the N-type Ca2+ channel via pertussis toxin-sensitive G proteins in NG108-15 cells and that this coupling is associated with rapid and homologous desensitization.