Differential activation and trafficking of μ-opioid receptors in brain slices

被引:90
作者
Arttamangkul, Seksiri [1 ]
Quillinan, Nidia [1 ]
Low, Malcolm J. [2 ]
von Zastrow, Mark [3 ]
Pintar, John [4 ]
Williams, John T. [1 ]
机构
[1] Oregon Hlth & Sci Univ, Vollum Inst, Portland, OR 97239 USA
[2] Oregon Hlth & Sci Univ, Ctr Study Weight Regulat, Dept Behav Neurosci, Portland, OR 97239 USA
[3] Univ Calif San Francisco, Dept Psychiat & Cellular & Mol Pharmacol, San Francisco, CA 94143 USA
[4] Univ Med & Dent New Jersey, Robert Wood Johnson Med Sch, Dept Neurosci & Cell Biol, Piscataway, NJ 08854 USA
关键词
D O I
10.1124/mol.108.048512
中图分类号
R9 [药学];
学科分类号
1007 ;
摘要
The activation of G protein-coupled receptors results in a cascade of events that include acute signaling, desensitization, and internalization, and it is thought that not all agonists affect each process to the same extent. The early steps in opioid receptor signaling, including desensitization, have been characterized electrophysiologically using brain slice preparations, whereas most previous studies of opioid receptor trafficking have been conducted in heterologous cell models. This study used transgenic mice that express an epitope-tagged (FLAG) mu-opioid receptor (FLAGMOR) targeted to catecholamine neurons by regulatory elements from the tyrosine hydroxylase gene. Brain slices from these mice were used to study tagged MOR receptors in neurons of the locus ceruleus. Activation of the FLAGMOR with [Met(5)] enkephalin (ME) produced a hyperpolarization that desensitized acutely to the same extent as native MOR in slices from wild-type mice. A series of opioid agonists were then used to study desensitization and receptor trafficking in brain slices, which was monitored with a monoclonal antibody against the FLAG epitope (M1) conjugated to Alexa 594. Three patterns of receptor trafficking and desensitization were observed: 1) ME, etorphine, and methadone resulted in both receptor desensitization and internalization; 2) morphine and oxymorphone caused significant desensitization without evidence for internalization; and 3) oxycodone was ineffective in both processes. These results show that two distinct forms of signaling were differentially engaged depending on the agonist used to activate the receptor, and they support the hypothesis that ligand-specific regulation of opioid receptors occurs in neurons maintained in brain slices from adult animals.
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收藏
页码:972 / 979
页数:8
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