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

Seksiri Arttamangkul, Nidia Quillinan, Malcolm J. Low, Mark Von Zastrow, John Pintar, John Williams

Research output: Contribution to journalArticle

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Abstract

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 trans-genic 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 FLAG-MOR with [Met5]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.

Original languageEnglish (US)
Pages (from-to)972-979
Number of pages8
JournalMolecular Pharmacology
Volume74
Issue number4
DOIs
StatePublished - Oct 2008

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Opioid Receptors
Enkephalins
Brain
Neurons
Epitopes
Oxymorphone
Etorphine
Oxycodone
Locus Coeruleus
Methadone
Tyrosine 3-Monooxygenase
G-Protein-Coupled Receptors
Morphine
Opioid Analgesics
Catecholamines
Monoclonal Antibodies
Ligands
Genes

ASJC Scopus subject areas

  • Pharmacology
  • Molecular Medicine

Cite this

Differential activation and trafficking of μ-opioid receptors in brain slices. / Arttamangkul, Seksiri; Quillinan, Nidia; Low, Malcolm J.; Von Zastrow, Mark; Pintar, John; Williams, John.

In: Molecular Pharmacology, Vol. 74, No. 4, 10.2008, p. 972-979.

Research output: Contribution to journalArticle

Arttamangkul, Seksiri ; Quillinan, Nidia ; Low, Malcolm J. ; Von Zastrow, Mark ; Pintar, John ; Williams, John. / Differential activation and trafficking of μ-opioid receptors in brain slices. In: Molecular Pharmacology. 2008 ; Vol. 74, No. 4. pp. 972-979.
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