Gene Symbol: Oprm1
Description: opioid receptor, mu 1
Alias: M-OR-1, MOP-R, MOR-1, MOR-1O, Oprm, mor, muOR, mu-type opioid receptor, MOP receptor, mu opioid receptor MOR-1BI, mu opioid receptor MOR-1P, mu opioid receptor splice variant mMOR-1Z
Species: mouse
Products:     Oprm1

Top Publications

  1. Gupta A, Mulder J, Gomes I, Rozenfeld R, Bushlin I, Ong E, et al. Increased abundance of opioid receptor heteromers after chronic morphine administration. Sci Signal. 2010;3:ra54 pubmed publisher
    ..Because of its distinct signaling properties, the mu-delta heteromer could be a therapeutic target in the treatment of chronic pain and addiction. ..
  2. Matthes H, Maldonado R, Simonin F, Valverde O, Slowe S, Kitchen I, et al. Loss of morphine-induced analgesia, reward effect and withdrawal symptoms in mice lacking the mu-opioid-receptor gene. Nature. 1996;383:819-23 pubmed
    ..We conclude that the mu-opioid-receptor gene product is the molecular target of morphine in vivo and that it is a mandatory component of the opioid system for morphine action...
  3. Scherrer G, Imamachi N, Cao Y, Contet C, Mennicken F, O donnell D, et al. Dissociation of the opioid receptor mechanisms that control mechanical and heat pain. Cell. 2009;137:1148-59 pubmed publisher
    ..Using a DOReGFP reporter mouse we now show that the DOR and MOR are, in fact, expressed by different subsets of primary afferents...
  4. Wang W, Loh H, Law P. The intracellular trafficking of opioid receptors directed by carboxyl tail and a di-leucine motif in Neuro2A cells. J Biol Chem. 2003;278:36848-58 pubmed
    The mu- and delta-opioid receptors (MOR and DOR) differ significantly in their intracellular trafficking...
  5. Wu Q, Hwang C, Yao S, Law P, Loh H, Wei L. A major species of mouse mu-opioid receptor mRNA and its promoter-dependent functional polyadenylation signal. Mol Pharmacol. 2005;68:279-85 pubmed
    The pharmacological effects of opioid drugs are mediated mainly by the mu-opioid receptor (MOR), which is encoded by an mRNA transcript named MOR1...
  6. Manglik A, Kruse A, Kobilka T, Thian F, Mathiesen J, Sunahara R, et al. Crystal structure of the µ-opioid receptor bound to a morphinan antagonist. Nature. 2012;485:321-6 pubmed publisher
    ..These high-resolution insights into opioid receptor structure will enable the application of structure-based approaches to develop better drugs for the management of pain and addiction. ..
  7. Liu X, Liu Z, Sun Y, Ross M, Kim S, Tsai F, et al. Unidirectional cross-activation of GRPR by MOR1D uncouples itch and analgesia induced by opioids. Cell. 2011;147:447-58 pubmed publisher
    ..We now report that the ?-opioid receptor (MOR) isoform MOR1D is essential for morphine-induced scratching (MIS), whereas the isoform MOR1 is required only for ..
  8. Reyes A, Levenson R, Berrettini W, Van Bockstaele E. Ultrastructural relationship between the mu opioid receptor and its interacting protein, GPR177, in striatal neurons. Brain Res. 2010;1358:71-80 pubmed publisher
    ..the mammalian ortholog of Drosophila Wntless/Evi/Sprinter, was recently identified as a novel mu-opioid receptor (MOR) interacting protein...
  9. Wang H, Zhao B, Zhong Y, Li K, Li Z, Wang Q, et al. Coexpression of delta- and mu-opioid receptors in nociceptive sensory neurons. Proc Natl Acad Sci U S A. 2010;107:13117-22 pubmed publisher
    ..Importantly, both DOR and MOR agonists reduce depolarization-induced Ca(2+) currents in single small DRG neurons and inhibit afferent C-fiber ..

More Information


  1. Liao D, Lin H, Law P, Loh H. Mu-opioid receptors modulate the stability of dendritic spines. Proc Natl Acad Sci U S A. 2005;102:1725-30 pubmed
    ..By activating ubiquitously clustered mu-opioid receptor (MOR) in excitatory synapses, morphine caused collapse of preexisting dendritic spines and decreased synaptic alpha-..
  2. Kim C, Hwang C, Choi H, Song K, Law P, Wei L, et al. Neuron-restrictive silencer factor (NRSF) functions as a repressor in neuronal cells to regulate the mu opioid receptor gene. J Biol Chem. 2004;279:46464-73 pubmed
    The mu opioid receptor (MOR) is expressed in the central nervous system and specific cell lines with varying expression levels perhaps playing important roles...
  3. Tien L, Park Y, Fan L, Ma T, Loh H, Ho I. Increased dopamine D2 receptor binding and enhanced apomorphine-induced locomotor activity in mu-opioid receptor knockout mice. Brain Res Bull. 2003;61:109-15 pubmed
    ..The enhanced locomotor activity may be related to the compensatory up-regulation of D2 dopamine receptors in mice lacking mu-opioid receptor genes. ..
  4. Pan Y, Xu J, Mahurter L, Bolan E, Xu M, Pasternak G. Generation of the mu opioid receptor (MOR-1) protein by three new splice variants of the Oprm gene. Proc Natl Acad Sci U S A. 2001;98:14084-9 pubmed
    Using 5' RACE, we have isolated four additional exons of the mu opioid receptor gene (Oprm), resulting in a gene spanning over 250 kb...
  5. Ko J, Minnerath S, Loh H. Dual promoters of mouse mu-opioid receptor gene. Biochem Biophys Res Commun. 1997;234:351-7 pubmed
    ..We found that receptor mRNA was predominantly initiated by the proximal promoter. These studies suggested that the proximal promoter was the major functional promoter. ..
  6. Slowe S, Simonin F, Kieffer B, Kitchen I. Quantitative autoradiography of mu-,delta- and kappa1 opioid receptors in kappa-opioid receptor knockout mice. Brain Res. 1999;818:335-45 pubmed
    ..This effect was most notable in the nucleus accumbens and the vertical limb of the diagonal band, and suggests there may be functional interactions between mu- and delta-receptors and kappa1- and delta-receptors in mouse brain. ..
  7. Song K, Hwang C, Kim C, Choi H, Law P, Wei L, et al. Translational repression of mouse mu opioid receptor expression via leaky scanning. Nucleic Acids Res. 2007;35:1501-13 pubmed
    Mu opioid receptor (MOR) expression is under temporal and spatial controls, but expression levels of the MOR gene are relatively low in vivo...
  8. Roberts A, McDonald J, Heyser C, Kieffer B, Matthes H, Koob G, et al. mu-Opioid receptor knockout mice do not self-administer alcohol. J Pharmacol Exp Ther. 2000;293:1002-8 pubmed
    ..These data provide new evidence for a critical role for mu-opioid receptors in ethanol self-administration assessed with a variety of behavioral paradigms and new insights into the neuropharmacological basis for ethanol reinforcement. ..
  9. Kozak C, Filie J, Adamson M, Chen Y, Yu L. Murine chromosomal location of the mu and kappa opioid receptor genes. Genomics. 1994;21:659-61 pubmed
    ..Multilocus cross analysis located the mu receptor gene Oprm on Chr 10 and the kappa receptor gene Oprk1 on Chr 1...
  10. Borgland S, Connor M, Osborne P, Furness J, Christie M. Opioid agonists have different efficacy profiles for G protein activation, rapid desensitization, and endocytosis of mu-opioid receptors. J Biol Chem. 2003;278:18776-84 pubmed
  11. Rodríguez Muñoz M, de la Torre Madrid E, Sánchez Blázquez P, Wang J, Garzón J. NMDAR-nNOS generated zinc recruits PKCgamma to the HINT1-RGS17 complex bound to the C terminus of Mu-opioid receptors. Cell Signal. 2008;20:1855-64 pubmed publisher
    In neurons, the C terminus of the Mu-opioid receptor (MOR) binds to the protein kinase C-interacting protein/histidine triad nucleotide binding protein 1 (PKCI/HINT1) which in turn binds the regulator of G-protein signalling RGSZ1/Z2 (..
  12. Roy S, Liu H, Loh H. mu-Opioid receptor-knockout mice: the role of mu-opioid receptor in gastrointestinal transit. Brain Res Mol Brain Res. 1998;56:281-3 pubmed
    The role of mu-opioid receptor in gastrointestinal transit was investigated using mu-opioid receptor knockout mice (MOR-KO)...
  13. Rossi G, Pan Y, Brown G, Pasternak G. Antisense mapping the MOR-1 opioid receptor: evidence for alternative splicing and a novel morphine-6 beta-glucuronide receptor. FEBS Lett. 1995;369:192-6 pubmed
    Although MOR-1 encodes a mu opioid receptor, its relationship to the pharmacologically defined mu receptor subtypes has been unclear. Antisense mapping now suggests that these subtypes result from alternative splicing of MOR-1...
  14. Loh H, Liu H, Cavalli A, Yang W, Chen Y, Wei L. mu Opioid receptor knockout in mice: effects on ligand-induced analgesia and morphine lethality. Brain Res Mol Brain Res. 1998;54:321-6 pubmed
    The mu opioid receptor gene (MOR) was mutated in mice by a gene targeting procedure...
  15. Groer C, Schmid C, Jaeger A, Bohn L. Agonist-directed interactions with specific beta-arrestins determine mu-opioid receptor trafficking, ubiquitination, and dephosphorylation. J Biol Chem. 2011;286:31731-41 pubmed publisher
    Morphine and other opiates mediate their effects through activation of the ?-opioid receptor (MOR), and regulation of the MOR has been shown to critically affect receptor responsiveness...
  16. Choi H, Hwang C, Kim C, Song K, Law P, Loh H, et al. Transcriptional regulation of mouse mu opioid receptor gene in neuronal cells by poly(ADP-ribose) polymerase-1. J Cell Mol Med. 2008;12:2319-33 pubmed publisher
    ..actions of morphine and morphine-like drugs such as heroin mediate primarily through the mu opioid receptor (MOR). It represents the target of the most valuable painkiller in contemporary medicine...
  17. Papaleo F, Kieffer B, Tabarin A, Contarino A. Decreased motivation to eat in mu-opioid receptor-deficient mice. Eur J Neurosci. 2007;25:3398-405 pubmed
    ..To assess the role for the micro-opioid receptor (MOR) pathway in the motivational properties of food intake, in the present study we tested wild-type and MOR-deficient ..
  18. Zhang Y, Pan Y, Kolesnikov Y, Pasternak G. Immunohistochemical labeling of the mu opioid receptor carboxy terminal splice variant mMOR-1B4 in the mouse central nervous system. Brain Res. 2006;1099:33-43 pubmed
    The mu opioid receptor gene Oprm is alternatively spliced into many variants, providing for the multiplicity of mu opioid receptor subtypes...
  19. Kim J, Bartlett S, He L, Nielsen C, Chang A, Kharazia V, et al. Morphine-induced receptor endocytosis in a novel knockin mouse reduces tolerance and dependence. Curr Biol. 2008;18:129-35 pubmed publisher
    ..These data suggest that opioid drugs with a pharmacological profile similar to morphine but the ability to promote endocytosis could provide analgesia while having a reduced liability for promoting tolerance and dependence. ..
  20. Law P, Erickson Herbrandson L, Zha Q, Solberg J, Chu J, Sarre A, et al. Heterodimerization of mu- and delta-opioid receptors occurs at the cell surface only and requires receptor-G protein interactions. J Biol Chem. 2005;280:11152-64 pubmed
    ..by producing the phenotypes of the 1:1 heterodimers formed between the constitutively expressed mu-opioid receptor (MOR) and the ponasterone A-induced expression of delta-opioid receptor (DOR) in EcR293 cells...
  21. Kaufman D, Keith D, Anton B, Tian J, Magendzo K, Newman D, et al. Characterization of the murine mu opioid receptor gene. J Biol Chem. 1995;270:15877-83 pubmed
  22. Hwang C, Wu X, Wang G, Kim C, Loh H. Mouse mu opioid receptor distal promoter transcriptional regulation by SOX proteins. J Biol Chem. 2003;278:3742-50 pubmed
    ..factors that bind to specific sequences in 5'-distal promoter regulatory sequences of the mouse mu opioid receptor (mor) promoter using the yeast one-hybrid system...
  23. Tanowitz M, Hislop J, von Zastrow M. Alternative splicing determines the post-endocytic sorting fate of G-protein-coupled receptors. J Biol Chem. 2008;283:35614-21 pubmed publisher
    ..To our knowledge the present results are the first to establish a role of alternative RNA processing in specifying the post-endocytic sorting of G-protein-coupled receptors between divergent and functionally distinct membrane pathways. ..
  24. Breslow J, Feng P, Meissler J, Pintar J, Gaughan J, Adler M, et al. Potentiating effect of morphine on oral Salmonella enterica serovar Typhimurium infection is ?-opioid receptor-dependent. Microb Pathog. 2010;49:330-5 pubmed publisher
    ..These results provide definitive evidence that the morphine-mediated enhancement of oral Salmonella infection is dependent on the ?-opioid receptor. ..
  25. Moorman J, Zhang Y, Liu B, Lesage G, Chen Y, Stuart C, et al. HIV-1 gp120 primes lymphocytes for opioid-induced, beta-arrestin 2-dependent apoptosis. Biochim Biophys Acta. 2009;1793:1366-71 pubmed publisher
    ..These data suggest a novel mechanism by which HIV-1 gp120 and opioids induce lymphocyte cell death. ..
  26. Sora I, Takahashi N, Funada M, Ujike H, Revay R, Donovan D, et al. Opiate receptor knockout mice define mu receptor roles in endogenous nociceptive responses and morphine-induced analgesia. Proc Natl Acad Sci U S A. 1997;94:1544-9 pubmed
  27. He L, Kim J, Whistler J. Biomarkers of morphine tolerance and dependence are prevented by morphine-induced endocytosis of a mutant mu-opioid receptor. FASEB J. 2009;23:4327-34 pubmed publisher
    Growing evidence shows that trafficking of the mu-opioid receptor (MOR) is a critical process in functional recovery from desensitization following activation and plays important roles in morphine tolerance and dependence largely because ..
  28. Giros B, Pohl M, Rochelle J, Seldin M. Chromosomal localization of opioid peptide and receptor genes in the mouse. Life Sci. 1995;56:PL369-75 pubmed
    ..In this study, we completed the localization on mouse chromosomes of the genes encoding mu (Oprm) and kappa (Oprk) receptors, as well as the genes for the opioid propeptides proenkephalin (Penk) and prodynorphin (..
  29. Arttamangkul S, Quillinan N, Low M, von Zastrow M, Pintar J, Williams J. Differential activation and trafficking of micro-opioid receptors in brain slices. Mol Pharmacol. 2008;74:972-9 pubmed publisher
    ..Brain slices from these mice were used to study tagged MOR receptors in neurons of the locus ceruleus...
  30. Doyle G, Sheng X, Lin S, Press D, Grice D, Buono R, et al. Identification of five mouse mu-opioid receptor (MOR) gene (Oprm1) splice variants containing a newly identified alternatively spliced exon. Gene. 2007;395:98-107 pubmed
    The mouse mu-opioid receptor gene, Oprm1, currently contains 18 recognized alternatively spliced exons [Doyle, G.A., Sheng, X.R., Lin, S.S.J., Press, D.M., Grice, D.E., Buono, R.J., Ferraro, T.N., Berrettini, W.H., 2007...
  31. Hwang C, Kim C, Choi H, McKercher S, Loh H. Transcriptional regulation of mouse mu opioid receptor gene by PU.1. J Biol Chem. 2004;279:19764-74 pubmed
    We previously reported that the 34-bp cis-acting element of the mouse micro opioid receptor (MOR) gene represses transcription of the MOR gene from the distal promoter...
  32. Ghozland S, Matthes H, Simonin F, Filliol D, Kieffer B, Maldonado R. Motivational effects of cannabinoids are mediated by mu-opioid and kappa-opioid receptors. J Neurosci. 2002;22:1146-54 pubmed
    ..Thus, an opposing activity of mu- and kappa-opioid receptors in modulating reward pathways forms the basis for the dual euphoric-dysphoric activity of THC. ..
  33. Roy S, Barke R, Loh H. MU-opioid receptor-knockout mice: role of mu-opioid receptor in morphine mediated immune functions. Brain Res Mol Brain Res. 1998;61:190-4 pubmed
    The role of the mu-opioid receptor in immune function was investigated using mu-opioid receptor knockout mice (MOR-KO)...
  34. Pan Y, Xu J, Bolan E, Chang A, Mahurter L, Rossi G, et al. Isolation and expression of a novel alternatively spliced mu opioid receptor isoform, MOR-1F. FEBS Lett. 2000;466:337-40 pubmed
    The MOR-1 gene is large, with a recent study reporting nine exons spanning 250 kb which combine to yield six different mu opioid receptor splice variants...
  35. Kim C, Choi H, Hwang C, Song K, Lee B, Law P, et al. Evidence of the neuron-restrictive silencer factor (NRSF) interaction with Sp3 and its synergic repression to the mu opioid receptor (MOR) gene. Nucleic Acids Res. 2006;34:6392-403 pubmed
    Previously, we reported that the neuron-restrictive silencer element (NRSE) of mu opioid receptor (MOR) functions as a critical regulator to repress the MOR transcription in specific neuronal cells, depending on neuron-restriction ..
  36. Ghozland S, Chu K, Kieffer B, Roberts A. Lack of stimulant and anxiolytic-like effects of ethanol and accelerated development of ethanol dependence in mu-opioid receptor knockout mice. Neuropharmacology. 2005;49:493-501 pubmed
    ..Mice lacking the mu-opioid receptor (MOR) do not self-administer ethanol and display decreased anxiety-like behavior...
  37. Chefer V, Kieffer B, Shippenberg T. Basal and morphine-evoked dopaminergic neurotransmission in the nucleus accumbens of MOR- and DOR-knockout mice. Eur J Neurosci. 2003;18:1915-22 pubmed
    ..rate of DA uptake, in the nucleus accumbens (NAc) of wild-type mice and those with a constitutive deletion of mu (MOR)- or delta (DOR)-opioid receptors. Locomotor activity was assessed in these same animals...
  38. Chang A, Emmel D, Rossi G, Pasternak G. Methadone analgesia in morphine-insensitive CXBK mice. Eur J Pharmacol. 1998;351:189-91 pubmed
    ..These results reveal distinct analgesic mechanisms for morphine and methadone and provide further support for multiple subtypes of mu-opioid receptors. ..
  39. Min B, Augustin L, Felsheim R, Fuchs J, Loh H. Genomic structure analysis of promoter sequence of a mouse mu opioid receptor gene. Proc Natl Acad Sci U S A. 1994;91:9081-5 pubmed
    We have isolated mouse mu opioid receptor genomic clones (termed MOR) containing the entire amino acid coding sequence corresponding to rat MOR-1 cDNA, including additional 5' flanking sequence...
  40. Pan Y, Xu J, Xu M, Rossi G, Matulonis J, Pasternak G. Involvement of exon 11-associated variants of the mu opioid receptor MOR-1 in heroin, but not morphine, actions. Proc Natl Acad Sci U S A. 2009;106:4917-22 pubmed publisher
    ..Like morphine, heroin has high affinity and selectivity for mu-receptors, but its residual analgesia in exon 1 MOR-1 knockout mice that do not respond to morphine suggests a different mechanism of action...
  41. Hwang C, Song K, Kim C, Choi H, Guo X, Law P, et al. Epigenetic programming of mu-opioid receptor gene in mouse brain is regulated by MeCP2 and Brg1 chromatin remodelling factor. J Cell Mol Med. 2009;13:3591-615 pubmed publisher
    The pharmacological action of morphine as a pain medication is mediated primarily through the mu-opioid receptor (MOR). With few exceptions, MOR is expressed in brain regions where opioid actions take place...
  42. Chefer V, Denoroy L, Zapata A, Shippenberg T. Mu opioid receptor modulation of somatodendritic dopamine overflow: GABAergic and glutamatergic mechanisms. Eur J Neurosci. 2009;30:272-8 pubmed publisher
    Mu opioid receptor (MOR) regulation of somatodendritic dopamine neurotransmission in the ventral tegmental area (VTA) was investigated using conventional microdialysis in freely moving rats and mice...
  43. Majumdar S, Grinnell S, Le Rouzic V, Burgman M, Polikar L, Ansonoff M, et al. Truncated G protein-coupled mu opioid receptor MOR-1 splice variants are targets for highly potent opioid analgesics lacking side effects. Proc Natl Acad Sci U S A. 2011;108:19778-83 pubmed publisher
    ..that this agent acts through a truncated, six-transmembrane variant of the G protein-coupled mu opioid receptor MOR-1...
  44. Hwang C, Song K, Kim C, Choi H, Guo X, Law P, et al. Evidence of endogenous mu opioid receptor regulation by epigenetic control of the promoters. Mol Cell Biol. 2007;27:4720-36 pubmed
    The pharmacological effect of morphine as a painkiller is mediated mainly via the mu opioid receptor (MOR) and is dependent on the number of MORs in the cell surface membrane...
  45. Raynor K, Kong H, Chen Y, Yasuda K, Yu L, Bell G, et al. Pharmacological characterization of the cloned kappa-, delta-, and mu-opioid receptors. Mol Pharmacol. 1994;45:330-4 pubmed
    ..The availability of the cloned receptors will facilitate the identification and development of more specific and selective compounds with greater therapeutic potential and fewer undesirable side effects. ..
  46. Hwang C, Kim C, Kim D, Law P, Wei L, Loh H. Up-regulation of the mu-opioid receptor gene is mediated through chromatin remodeling and transcriptional factors in differentiated neuronal cells. Mol Pharmacol. 2010;78:58-68 pubmed publisher
    The effects of morphine are mediated mainly through the mu opioid receptor (MOR)...
  47. Sargeant T, Day D, Mrkusich E, Foo D, Miller J. Mu opioid receptors are expressed on radial glia but not migrating neuroblasts in the late embryonic mouse brain. Brain Res. 2007;1175:28-38 pubmed
    ..Surprisingly, the distribution of the mu opioid receptor (MOR) in the embryonic brain, especially in proliferative regions, is poorly defined and subject to conflicting reports...
  48. Garzón J, Rodríguez Muñoz M, López Fando A, Sánchez Blázquez P. Activation of mu-opioid receptors transfers control of Galpha subunits to the regulator of G-protein signaling RGS9-2: role in receptor desensitization. J Biol Chem. 2005;280:8951-60 pubmed
    In mouse periaqueductal gray matter (PAG) membranes, the mu-opioid receptor (MOR) coprecipitated the alpha-subunits of the Gi/o/z/q/11 proteins, the Gbeta1/2 subunits, and the regulator of G-protein signaling RGS9-2 and its partner ..
  49. Moles A, Kieffer B, D Amato F. Deficit in attachment behavior in mice lacking the mu-opioid receptor gene. Science. 2004;304:1983-6 pubmed
    ..Results from this study may indicate a molecular mechanism for diseases characterized by deficits in attachment behavior, such as autism or reactive attachment disorder. ..
  50. Filliol D, Ghozland S, Chluba J, Martin M, Matthes H, Simonin F, et al. Mice deficient for delta- and mu-opioid receptors exhibit opposing alterations of emotional responses. Nat Genet. 2000;25:195-200 pubmed
    ..The mu-, delta- and kappa- opioid receptors (encoded by Oprm, Oprd1 and Oprk1, respectively) mediate the biological activity of opioids...
  51. Pan Y, Xu J, Bolan E, Abbadie C, Chang A, Zuckerman A, et al. Identification and characterization of three new alternatively spliced mu-opioid receptor isoforms. Mol Pharmacol. 1999;56:396-403 pubmed
    We have identified four new mu-opiod receptor (MOR)-1 exons, indicating that the gene now contains at least nine exons spanning more than 200 kilobases. Replacement of exon 4 by combinations of the new exons yields three new receptors...
  52. Jaferi A, Pickel V. Mu-opioid and corticotropin-releasing-factor receptors show largely postsynaptic co-expression, and separate presynaptic distributions, in the mouse central amygdala and bed nucleus of the stria terminalis. Neuroscience. 2009;159:526-39 pubmed publisher
    ..The commonalities in the synaptic location of both receptors in the CeA and BNST suggest that this is a fundamental cellular association of relevance to both drug addiction and stress-induced disorders. ..
  53. Tan M, Walwyn W, Evans C, Xie C. p38 MAPK and beta-arrestin 2 mediate functional interactions between endogenous micro-opioid and alpha2A-adrenergic receptors in neurons. J Biol Chem. 2009;284:6270-81 pubmed publisher