title: Protein kinase C-mediated inhibition of mu-opioid receptor internalization and its involvement in the development of acute tolerance to peripheral mu-agonist analgesia.
abstract: We investigated the role of protein kinase C (PKC) in cell mu-opioid receptor (MOR) internalization and MOR-mediated acute tolerance in vivo. When Chinese hamster ovary cells expressing MOR were exposed to [D-Ala(2),MePhe(4),Gly-ol(5)]-enkephalin (DAMGO), receptor internalization was observed at 30 min. Incubation with morphine failed to induce receptor internalization. When calphostin C, a PKC inhibitor, was added, receptor internalization was observed as early as 10 min after morphine stimulation. The MOR internalization induced by DAMGO or morphine in the presence of calphostin C was dynamin dependent, because it was abolished 2 d after pretreatment with recombinant adenovirus to express a dominant interfering dynamin mutant (K44A/dynamin adenovirus). On the other hand, in a peripheral nociception test in mice, the nociceptive flexor response after intraplantar injection (i.pl.) of bradykinin was markedly inhibited by DAMGO (i.pl.). DAMGO analgesia was not affected by 2 hr prior injection (i.pl.) of DAMGO. Marked acute tolerance was observed after pretreatment with dynamin antisense oligodeoxynucleotide or K44A/dynamin adenovirus. The DAMGO-induced acute tolerance under such pretreatments was inhibited by calphostin C. Together, these findings suggest that PKC desensitizes MOR or has a role in the development of acute tolerance through MOR by inhibiting internalization mechanisms as a resensitization process.
authors: Department of Molecular Pharmacology and Neuroscience, Nagasaki University School of Pharmaceutical Sciences, Nagasaki 852-8521, Japan. ueda@net.nagasaki-u.ac.jp
authors: H
authors: H
authors: Ueda
authors: M
authors: M
authors: Inoue
authors: T
authors: T
authors: Matsumoto
mesh_terms: D000698:Analgesia; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D019540:Area Under Curve; D016466:CHO Cells; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance / Q000235:genetics / Q000502:physiology*; D034281:Dynamins; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D005822:Genetic Vectors / Q000235:genetics / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009020:Morphine / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D017450:Receptors, Opioid, mu / Q000819:agonists / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D000701:Analgesics, Opioid; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D009281:Naphthalenes; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009020:Morphine; D011493:Protein Kinase C; D020558:GTP Phosphohydrolases; D034281:Dynamins; C058819:calphostin C