title: Differential in vivo internalization of MOR-1 and MOR-1C by morphine.
abstract: The mu opioid receptor MOR-1 is internalized by many mu agonists, but not morphine. To see whether differences in the intracellular carboxy terminus influences internalization, we examined internalization of a splice variant of the mu opioid receptor, MOR-1C, in the lateral septum of the mouse in vivo. Following intracerebroventricular (i.c.v.) saline treatment, MOR-1C-like immunoreactivity (LI) within neurons in naive mice was found predominantly in clusters close to the plasma membrane. Following either intracerebroventricular [d-Ala2, MePhe4,Gly(ol)5]enkephalin (DAMGO) or morphine, MOR-1C-LI clustered into endosomes in the cytoplasm. This effect was suppressed by prior administration of the opioid antagonist naloxone. In contrast, only DAMGO, and not morphine, internalized MOR-1-LI. These results illustrate differences in internalization between two MOR-1 variants that have alternative splicing at the COOH terminus.
authors.affiliation: Laboratory of Molecular Neuropharmacology, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA.
authors.forename: C
authors.initials: C
authors.lastname: Abbadie
authors.forename: G W
authors.initials: GW
authors.lastname: Pasternak
mesh_terms: D017398:Alternative Splicing / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000494:pharmacology; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D009020:Morphine / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020033:Protein Isoforms / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000235:genetics; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology*; D017450:Receptors, Opioid, mu / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D012686:Septal Nuclei / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D017450:Receptors, Opioid, mu; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D009270:Naloxone; D009020:Morphine