Desensitization and resensitization of delta-opioid receptor-mediated Ca2+ channel inhibition in NG108-15 cells

Br J Pharmacol. 1998 Mar;123(6):1111-8. doi: 10.1038/sj.bjp.0701733.


1. To approach the mechanisms underlying desensitization of the opioid receptor-mediated Ca2+ channel inhibition, the effects of prolonged application of [D-Ala2, D-Leu5]enkephalin (DADLE) on Ba2+ currents (I(Ba)) through Ca2+ channels were analysed in NG108-15 neuroblastoma x glioma hybrid cells. 2. Inhibition of I(Ba) by 100 nM DADLE desensitized by 57% with a time constant of 4.4 min. 3. Maximal desensitization of the delta-opioid receptor-Ca2+ channel coupling was attained by 1 microM DADLE. The EC50 value for desensitization was estimated to be 78 nM. 4. RNA blot hybridization analysis and immunoblot analysis revealed the expression of beta-adrenoceptor kinase-1 (betaARK1) in NG108-15 cells. 5. Heparin, an inhibitor of betaARK, significantly reduced the magnitude and rate of desensitization, whereas Rp-cyclic AMPS and PKI (14-24)amide, inhibitors of cyclic AMP-dependent protein kinase (PKA), or long-term treatment with phorbol 12-myristate 13-acetate to induce down-regulation of protein kinase C (PKC) had no significant effect. 6. Recovery from desensitization (resensitization) proceeded with a time constant of 6.7 min. Okadaic acid, an inhibitor of serine/threonine phosphatases 1 and 2A, significantly attenuated the degree of resensitization. 7. In summary, we have characterized the time course and concentration-dependence of the desensitization of DADLE-induced I(Ba) inhibition in NG108-15 cells. This desensitization was reversible after removal of DADLE. It is suggested that betaARK, but neither PKA nor PKC, is involved in desensitization, while serine/threonine phosphatases mediate resensitization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • COS Cells
  • Calcium Channel Blockers / pharmacology*
  • Cyclic AMP-Dependent Protein Kinases / genetics
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Dose-Response Relationship, Drug
  • Enkephalin, Leucine-2-Alanine / pharmacology*
  • Hybrid Cells
  • Protein Kinase C / metabolism
  • Receptors, Opioid, delta / drug effects*
  • Receptors, Opioid, delta / physiology
  • Tumor Cells, Cultured
  • beta-Adrenergic Receptor Kinases


  • Calcium Channel Blockers
  • Receptors, Opioid, delta
  • Enkephalin, Leucine-2-Alanine
  • Cyclic AMP-Dependent Protein Kinases
  • Protein Kinase C
  • beta-Adrenergic Receptor Kinases