Desensitization and resensitization of δ‐opioid receptor‐mediated Ca2+ channel inhibition in NG108‐15 cells

• Published in: British journal of pharmacology Vol. 123; no. 6; pp. 1111 - 1118
• Main Authors: Morikawa, Hitoshi, Fukuda, Kazuhiko, Mima, Hiroyuki, Shoda, Takehiro, Kato, Shigehisa, Mori, Kenjiro
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.03.1998; Nature Publishing
• Subjects: Animals; beta-Adrenergic Receptor Kinases; Biological and medical sciences; Calcium Channel Blockers - pharmacology; calcium channels; COS Cells; Cyclic AMP-Dependent Protein Kinases - genetics; Cyclic AMP-Dependent Protein Kinases - metabolism; desensitization; Dose-Response Relationship, Drug; Enkephalin, Leucine-2-Alanine - pharmacology; Hybrid Cells; Medical sciences; Neuropharmacology; Neurotransmitters. Neurotransmission. Receptors; NG108‐15 cells; opioid δ receptors; Opioids; patch clamp; Peptidergic system (neuropeptide, opioid peptide, opiates...). Adenosinergic and purinergic systems; Pharmacology. Drug treatments; Protein Kinase C - metabolism; Receptors, Opioid, delta - drug effects; Receptors, Opioid, delta - physiology; resensitization; Tumor Cells, Cultured; β‐adrenoceptor kinases; Cell culture; Phosphoprotein phosphatase; Enkephalin; Phosphoric monoester hydrolases; Electrophysiology; Patch clamp method; Opiates; Esterases; Ionic channel; Neuroblastoma; δ Opioid receptor; Dose activity relation; β-Adrenergic receptor; Malignant glioma; Established cell line; Sensitization; Tumor cell; Calcium Cations; Nervous system diseases; Desensitization; Enzyme; Transferases; Malignant tumor; In vitro; Protein kinase; Central nervous system disease; Hydrolases
• DOI: 10.1038/sj.bjp.0701733
• ISSN: 0007-1188

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 (IBa) through Ca2+ channels were analysed in NG108‐15 neuroblastoma × glioma hybrid cells. 2 Inhibition of IBa by 100 nM DADLE desensitized by 57% with a time constant of 4.4 min. 3 Maximal desensitization of the δ‐opioid receptor‐Ca2+ channel coupling was attained by 1 μM DADLE. The EC50 value for desensitization was estimated to be 78 nM. 4 RNA blot hybridization analysis and immunoblot analysis revealed the expression of β‐adrenoceptor kinase‐1 (βARK1) in NG108‐15 cells. 5 Heparin, an inhibitor of βARK, 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 IBa inhibition in NG108‐15 cells. This desensitization was reversible after removal of DADLE. It is suggested that βARK, but neither PKA nor PKC, is involved in desensitization, while serine/threonine phosphatases mediate resensitization. British Journal of Pharmacology (1998) 123, 1111–1118; doi:10.1038/sj.bjp.0701733