%0 Journal Article %A Emily R Leff %A Seksiri Arttamangkul %A John T Williams %T Chronic treatment with morphine disrupts acute kinase-dependent desensitization of GPCRs %D 2020 %R 10.1124/mol.119.119362 %J Molecular Pharmacology %P mol.119.119362 %X Based on studies using mutations of the µ-opioid receptor (MOR), phosphorylation of multiple sites on the C-terminus has been recognized as a critical step underlying acute desensitization and the development of cellular tolerance. The aim of this study is to explore which kinase(s) mediate desensitization of MOR in brain slices from drug naïve and morphine treated animals. Whole-cell recordings from locus coeruleus neurons were made and the agonist-induced increase in potassium conductance was measured. In slices from naïve animals, pharmacological inhibition of G-protein receptor kinase (GRK2/3) with compound 101 blocked acute desensitization. Following chronic treatment with morphine, compound 101 was less effective at blocking acute desensitization. Compound 101 blocked receptor internalization in tissue from both naïve and morphine treated animals suggesting that GRK2/3 remained active. Kinase inhibitors aimed at blocking PKC and JNK had no effect on desensitization in tissue taken from naïve animals. However, in slices taken from morphine treated animals, the combination of these blockers along with compound 101 was required to block acute desensitization. Acute desensitization of the potassium conductance induced by the somatostatin receptor was also blocked by compound 101 in slices from naïve but not morphine treated animals. As was observed with MOR, it was necessary to use the combination of kinase inhibitors to block desensitization of the somatostatin receptor in slices from morphine treated animals. The results show that chronic treatment with morphine results in a surprising and heterologous adaptation in kinase-dependent desensitization.SIGNIFICANCE STATEMENT The results show that chronic treatment with morphine induced heterologous adaptations in kinase regulation of GPCR desensitization. Although the canonical mechanism for acute desensitization through phosphorylation by GRKs is supported in tissue taken from naïve animals, following chronic treatment with morphine, the acute kinase-dependent desensitization of GPCRs is disrupted such that additional kinases, including PKC and JNK, contribute to desensitization. %U https://molpharm.aspetjournals.org/content/molpharm/early/2020/05/03/mol.119.119362.full.pdf