Top ▲

μ receptor

Click here for help

Target not currently curated in GtoImmuPdb

Target id: 319

Nomenclature: μ receptor

Family: Opioid receptors

Contents:

Gene and Protein Information Click here for help
class A G protein-coupled receptor
Species TM AA Chromosomal Location Gene Symbol Gene Name Reference
Human 7 400 6q25.2 OPRM1 opioid receptor mu 1 170
Mouse 7 398 10 1.85 cM Oprm1 opioid receptor, mu 1 107
Rat 7 398 1q11 Oprm1 opioid receptor, mu 1 25,45,152,169,180
Previous and Unofficial Names Click here for help
Mu receptor | MOP | OP3 | MOPr | opioid receptor, mu 1 | opioid receptor
Database Links Click here for help
Specialist databases
GPCRdb oprm_human (Hs), oprm_mouse (Mm), oprm_rat (Rn)
Other databases
Alphafold P35372 (Hs), P42866 (Mm), P33535 (Rn)
ChEMBL Target CHEMBL233 (Hs), CHEMBL2858 (Mm), CHEMBL270 (Rn)
DrugBank Target P35372 (Hs)
Ensembl Gene ENSG00000112038 (Hs), ENSMUSG00000000766 (Mm), ENSRNOG00000018191 (Rn)
Entrez Gene 4988 (Hs), 18390 (Mm), 25601 (Rn)
Human Protein Atlas ENSG00000112038 (Hs)
KEGG Gene hsa:4988 (Hs), mmu:18390 (Mm), rno:25601 (Rn)
OMIM 600018 (Hs)
Pharos P35372 (Hs)
RefSeq Nucleotide NM_000914 (Hs), NM_001039652 (Mm), NM_013071 (Rn)
RefSeq Protein NP_000905 (Hs), NP_001034741 (Mm), NP_037203 (Rn)
SynPHARM 3941 (in complex with β-FNA)
UniProtKB P35372 (Hs), P42866 (Mm), P33535 (Rn)
Wikipedia OPRM1 (Hs)
Selected 3D Structures Click here for help
Image of receptor 3D structure from RCSB PDB
Description:  Crystal structure of the mu-opioid receptor bound to a morphinan antagonist
PDB Id:  4DKL
Ligand:  β-FNA
Resolution:  2.8Å
Species:  Mouse
References:  95
Image of receptor 3D structure from RCSB PDB
Description:  Structure of the μ-opioid receptor–Gi protein complex
PDB Id:  6DDF
Ligand:  DAMGO
Resolution:  3.5Å
Species:  Mouse
References:  79
Natural/Endogenous Ligands Click here for help
dynorphin A-(1-13) {Sp: Human, Mouse, Rat}
dynorphin A {Sp: Human, Mouse, Rat}
dynorphin A-(1-8) {Sp: Human, Mouse, Rat}
dynorphin B {Sp: Human, Mouse, Rat}
endomorphin-1 {Sp: Human}
endomorphin-2 {Sp: Human}
β-endorphin {Sp: Human} , β-endorphin {Sp: Mouse} , β-endorphin {Sp: Rat}
[Leu]enkephalin {Sp: Human, Mouse, Rat}
[Met]enkephalin {Sp: Human, Mouse, Rat}
Comments: β-Endorphin is the highest potency endogenous ligand
Potential endogenous agonists
endomorphin-1, endomorphin-2
Principal endogenous agonists (Human)
β-endorphin (POMC, P01189), [Met]enkephalin (PENK, P01210), [Leu]enkephalin (PENK, P01210)

Download all structure-activity data for this target as a CSV file go icon to follow link

Agonists
Key to terms and symbols View all chemical structures Click column headers to sort
Ligand Sp. Action Value Parameter Reference
[3H]DAMGO Peptide Ligand is labelled Ligand is radioactive Rn Full agonist 9.2 pKd 134
⤷ pKd 9.2 (Kd 5.7x10-10 M) [134]
carfentanil Small molecule or natural product Click here for species-specific activity table Cp Agonist 10.6 pKi 33
⤷ pKi 10.6 (Ki 2.4x10-11 M) [33]
Description: Binding affinity in guinea pig whole brain- displacement of [3H]DAGO binding.
(-)-cyclazocine Small molecule or natural product Click here for species-specific activity table Hs Partial agonist 10.0 pKi 156
⤷ pKi 10.0 [156]
butorphanol Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Partial agonist 9.9 pKi 47
⤷ pKi 9.9 (Ki 1.2x10-10 M) [47]
Description: Displacement of [3H]DAMGO from human μ opioid receptor expressed in CHO cells.
sufentanil Small molecule or natural product Approved drug Primary target of this compound Hs Full agonist 9.9 pKi 165
⤷ pKi 9.9 (Ki 1.38x10-10 M) [165]
etonitazene Small molecule or natural product Click here for species-specific activity table Hs Full agonist 9.7 pKi 156
⤷ pKi 9.7 [156]
hydromorphone Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Agonist 9.6 pKi 171
⤷ pKi 9.6 (Ki 2.8x10-10 M) [171]
ethylketocyclazocine Small molecule or natural product Click here for species-specific activity table Hs Full agonist 9.5 pKi 156
⤷ pKi 9.5 [156]
etorphine Small molecule or natural product Click here for species-specific activity table Hs Full agonist 9.5 pKi 156
⤷ pKi 9.5 [156]
fentanyl Small molecule or natural product Approved drug Ligand has a PDB structure Rn Full agonist 9.4 pKi 134
⤷ pKi 9.4 [134]
DAMGO Peptide Click here for species-specific activity table Hs Full agonist 9.3 pKi 58,156
⤷ pKi 9.3 [58,156]
loperamide Small molecule or natural product Approved drug Primary target of this compound Hs Agonist 9.3 pKi 26
⤷ pKi 9.3 (Ki 5.3x10-10 M) [26]
(-)-methadone Small molecule or natural product Click here for species-specific activity table Hs Full agonist 9.2 pKi 156
⤷ pKi 9.2 [156]
[Met]enkephalin {Sp: Human, Mouse, Rat} Peptide Click here for species-specific activity table Ligand is endogenous in the given species Immunopharmacology Ligand Rn Full agonist 9.2 pKi 134
⤷ pKi 9.2 [134]
fentanyl Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Ligand has a PDB structure Hs Full agonist 9.2 pKi 156
⤷ pKi 9.2 [156]
cebranopadol Small molecule or natural product Click here for species-specific activity table Hs Agonist 9.1 pKi 90
⤷ pKi 9.1 (Ki 7x10-10 M) [90]
Description: Radioligand binding assay
sufentanil Small molecule or natural product Approved drug Rn Full agonist 9.1 pKi 174
⤷ pKi 9.1 (Ki 7.7x10-10 M) [174]
eluxadoline Small molecule or natural product Approved drug Click here for species-specific activity table Rn Agonist 9.1 pKi 18
⤷ pKi 9.1 (Ki 9x10-10 M) [18]
morphine Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Ligand has a PDB structure Hs Full agonist 9.0 pKi 52,156
⤷ pKi 9.0 [52,156]
β-endorphin {Sp: Human} Peptide Click here for species-specific activity table Rn Full agonist 9.0 pKi 134
⤷ pKi 9.0 [134]
PZM21 Small molecule or natural product Primary target of this compound Ligand has a PDB structure Hs Biased agonist 9.0 pKi 96
⤷ pKi 9.0 (Ki 1.1x10-9 M) [96]
bilorphin Small molecule or natural product Primary target of this compound Click here for species-specific activity table Hs Agonist 9.0 pKi 36
⤷ pKi 9.0 (Ki 1.1x10-9 M) [36]
dihydromorphine Small molecule or natural product Click here for species-specific activity table Hs Full agonist 8.8 pKi 156
⤷ pKi 8.8 [156]
dynorphin-(1-11) Peptide Click here for species-specific activity table Hs Full agonist 8.8 pKi 156
⤷ pKi 8.8 [156]
normorphine Small molecule or natural product Click here for species-specific activity table Hs Full agonist 8.8 pKi 156
⤷ pKi 8.8 [156]
nalbuphine Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Partial agonist 8.8 pKi 171
⤷ pKi 8.8 (Ki 1.6x10-9 M) [171]
buprenorphine Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Partial agonist 8.8 pKi 156
⤷ pKi 8.8 [156]
eluxadoline Small molecule or natural product Approved drug Hs Agonist 8.8 pKi 18
⤷ pKi 8.8 (Ki 1.7x10-9 M) [18]
DADLE Peptide Click here for species-specific activity table Hs Full agonist 8.7 pKi 156
⤷ pKi 8.7 [156]
DAMGO Peptide Click here for species-specific activity table Rn Full agonist 8.7 pKi 134
⤷ pKi 8.7 [134]
hydrocodone Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Agonist 8.7 pKi 121
⤷ pKi 8.7 (Ki 2x10-9 M) [121]
BU08028 Small molecule or natural product Click here for species-specific activity table Hs Partial agonist 8.7 pKi 74
⤷ pKi 8.7 (Ki 2.14x10-9 M) [74]
cebranopadol Small molecule or natural product Click here for species-specific activity table Rn Agonist 8.6 pKi 90
⤷ pKi 8.6 (Ki 2.4x10-9 M) [90]
Description: Radioligand binding assay
dynorphin B {Sp: Human, Mouse, Rat} Peptide Click here for species-specific activity table Ligand is endogenous in the given species Hs Full agonist 8.5 pKi 156
⤷ pKi 8.5 [156]
endomorphin-2 {Sp: Human} Peptide Ligand is endogenous in the given species Rn Full agonist 8.5 pKi 179
⤷ pKi 8.5 (Ki 3.24x10-9 M) [179]
(-)-pentazocine Small molecule or natural product Approved drug Click here for species-specific activity table Hs Partial agonist 8.4 pKi 156
⤷ pKi 8.4 [156]
dynorphin A-(1-8) {Sp: Human, Mouse, Rat} Peptide Click here for species-specific activity table Ligand is endogenous in the given species Hs Full agonist 8.4 pKi 156
⤷ pKi 8.4 [156]
dynorphin A-(1-13) {Sp: Human, Mouse, Rat} Peptide Click here for species-specific activity table Ligand is endogenous in the given species Hs Full agonist 8.3 pKi 156
⤷ pKi 8.3 [156]
endomorphin-1 {Sp: Human} Peptide Click here for species-specific activity table Ligand is endogenous in the given species Hs Full agonist 8.3 pKi 54,179
⤷ pKi 8.3 (Ki 5.01x10-9 M) [54,179]
DSLET Peptide Click here for species-specific activity table Hs Full agonist 8.2 pKi 156
⤷ pKi 8.2 [156]
PL017 Peptide Hs Full agonist 8.2 pKi 23,156
⤷ pKi 8.2 [23,156]
[Leu]enkephalin {Sp: Human, Mouse, Rat} Peptide Click here for species-specific activity table Ligand is endogenous in the given species Hs Partial agonist 8.1 pKi 156
⤷ pKi 8.1 [156]
dynorphin A {Sp: Human, Mouse, Rat} Peptide Click here for species-specific activity table Ligand is endogenous in the given species Hs Full agonist 8.1 pKi 156
⤷ pKi 8.1 [156]
UFP-512 Small molecule or natural product Click here for species-specific activity table Hs Agonist 8.0 pKi 164
⤷ pKi 8.0 [164]
Description: Measuring displacement of [3H]-diprenorphine in vitro
morphine Small molecule or natural product Approved drug Click here for species-specific activity table Ligand has a PDB structure Rn Partial agonist 7.9 pKi 134
⤷ pKi 7.9 [134]
BW373U86 Small molecule or natural product Click here for species-specific activity table Rn Agonist 7.8 pKi 22
⤷ pKi 7.8 (Ki 1.5x10-8 M) [22]
UFP-505 Small molecule or natural product Click here for species-specific activity table Hs Agonist 7.8 pKi 38-39
⤷ pKi 7.8 [38-39]
ADL5747 Small molecule or natural product Click here for species-specific activity table Hs Agonist 7.7 pKi 85
⤷ pKi 7.7 (Ki 1.8x10-8 M) [85]
SRI22141 Small molecule or natural product Click here for species-specific activity table Hs Agonist 7.7 pKi 87
⤷ pKi 7.7 (Ki 1.97x10-8 M) [87]
Description: Binding affinity
ADL5859 Small molecule or natural product Click here for species-specific activity table Hs Agonist 7.5 pKi 84
⤷ pKi 7.5 (Ki 3.2x10-8 M) [84]
ICI-199441 Small molecule or natural product Click here for species-specific activity table Hs Agonist 7.3 pKi 81
⤷ pKi 7.3 (Ki 5.3x10-8 M) [81]
Description: Displacement of [3H]diprenorphine from human μ opioid receptor expressed in CHO-K1 cells
SCH221510 Small molecule or natural product Click here for species-specific activity table Hs Agonist 7.2 pKi 163
⤷ pKi 7.2 (Ki 6.5x10-8 M) [163]
Description: Radioligand binding assay
SR16835 Small molecule or natural product Click here for species-specific activity table Hs Agonist 7.1 pKi 157
⤷ pKi 7.1 (Ki 7.99x10-8 M) [157]
Description: Radioligand binding assay
codeine Small molecule or natural product Approved drug Primary target of this compound Hs Full agonist 6.9 pKi 156
⤷ pKi 6.9 [156]
tapentadol Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Agonist 6.8 pKi 159
⤷ pKi 6.8 (Ki 1.6x10-7 M) [159]
oxycodegol Small molecule or natural product Click here for species-specific activity table Hs Agonist 6.6 pKi 110
⤷ pKi 6.6 (Ki 2.37x10-7 M) [110]
Description: Competitive membrane binding assay measuring displacement [3H]naloxone from human μ receptors expressed by CHO cells.
BW373U86 Small molecule or natural product Click here for species-specific activity table Hs Agonist 6.6 pKi 84
⤷ pKi 6.6 (Ki 2.6x10-7 M) [84]
HS665 Small molecule or natural product Click here for species-specific activity table Hs Agonist 6.3 pKi 147
⤷ pKi 6.3 (Ki 5.42x10-7 M) [147]
compound 3 [PMID: 23134120] Small molecule or natural product Click here for species-specific activity table Hs Agonist 6.1 pKi 147
⤷ pKi 6.1 (Ki 8.26x10-7 M) [147]
tramadol Small molecule or natural product Approved drug Click here for species-specific activity table Hs Agonist 5.8 pKi 171
⤷ pKi 5.8 (Ki 1.6x10-6 M) [171]
Description: Displacement of the mu aginist peptide DAMGO from the mu receptor expressed in CHO cells.
SRI22141 Small molecule or natural product Click here for species-specific activity table Hs Agonist 9.7 pEC50 87
⤷ pEC50 9.7 (EC50 2x10-10 M) [87]
Description: Potency in a 35S-GTPγS assay
PZM21 Small molecule or natural product Primary target of this compound Ligand has a PDB structure Hs Biased agonist 8.3 pEC50 96
⤷ pEC50 8.3 (EC50 4.6x10-9 M) [96]
Description: In a Gi/o activation assay.
4F-MT-45 Small molecule or natural product Hs Agonist 6.8 pEC50 8
⤷ pEC50 6.8 (EC50 1.7x10-7 M) [8]
Description: β-arrestin2 recruitment assay
2F-MT-45 Small molecule or natural product Hs Agonist 6.7 pEC50 8
⤷ pEC50 6.7 (EC50 2x10-7 M) [8]
Description: β-arrestin2 recruitment assay
3F-MT-45 Small molecule or natural product Hs Agonist 6.2 pEC50 8
⤷ pEC50 6.2 (EC50 6.1x10-7 M) [8]
Description: β-arrestin2 recruitment assay
MT-45 Small molecule or natural product Hs Agonist 4.6 pEC50 8
⤷ pEC50 4.6 (EC50 2.3x10-5 M) [8]
Description: β-arrestin2 recruitment assay
levorphanol Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Agonist 9.9 pIC50 60
⤷ pIC50 9.9 (IC50 1.3x10-10 M) [60]
BU72 Small molecule or natural product Ligand has a PDB structure Cp Agonist 9.8 pIC50 65
⤷ pIC50 9.8 (IC50 1.5x10-10 M) [65]
Description: Measuring displacement of [3H]DAMGO from brain membranes isolated from Hartley guinea pigs.
methadone Small molecule or natural product Approved drug Primary target of this compound Hs Agonist 8.4 pIC50 132
⤷ pIC50 8.4 (IC50 4.1x10-9 M) [132]
Description: Binding affinity against μ-opioid receptor (human) using [3H]DAMGO radioligand.
pethidine Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Agonist 6.5 pIC50 132
⤷ pIC50 6.5 (IC50 3.15x10-7 M) [132]
AR-M1000390 Small molecule or natural product Click here for species-specific activity table Hs Agonist 5.4 pIC50 4
⤷ pIC50 5.4 (IC50 3.8x10-6 M) [4]
[3H]PL017 Peptide Ligand is labelled Ligand is radioactive Rn Agonist - - 61
⤷ [61]
U-47700 Small molecule or natural product Rn Agonist - - 27
⤷ [27]
View species-specific agonist tables
Agonist Comments
Discrimination of full or partial agonism is very dependent on the level of receptor expression and on the assay used to monitor agonist effects. Many agents may behave as full agonists or potent partial agonists in cell lines expressing cloned receptors in high concentration, but in other environments they may show only weak agonist activity. The identification of agonist activity in the table is largely based on the ability to stimulate GTPγ35S binding in cell lines expressing cloned human μ receptors. Agents giving 85% or greater stimulation than that given by DAMGO have been characterized as Full Agonists [156].

It is still unclear whether endomorphins are endogenous. Morphine occurs endogenously [131].

We have tagged the μ receptor as the primary drug target for hydrocodone based on this drug having the highest affinity at this receptor compared to the κ and δ receptors [121]. Similarly, we have tagged the μ receptor as the primary target of hydromorphone [171].

Methadone is selective for the μ receptor: comparable IC50s at the κ and δ receptors are 512 and 1090nM respectively [132].

[11C]carfentanil (PubChem CID 449698) binds the human μ receptor with a Ki of 0.07 nM, in a [3H]DAMGO displacement assay [62].
Antagonists
Key to terms and symbols View all chemical structures Click column headers to sort
Ligand Sp. Action Value Parameter Reference
[3H]diprenorphine Small molecule or natural product Ligand is labelled Ligand is radioactive Mm Antagonist 10.1 pKd 134
⤷ pKd 10.1 (Kd 7.94x10-11 M) [134]
[3H]naloxone Small molecule or natural product Ligand is labelled Ligand is radioactive Rn Antagonist 8.6 – 9.0 pKd 123
⤷ pKd 8.6 – 9.0 (Kd 2.8x10-9 – 1x10-9 M) [123]
Description: CHO and BHK cell lines stably expressing the rat μ receptor
naloxonazine Small molecule or natural product Mm Antagonist 10.3 pKi 134
⤷ pKi 10.3 [134]
samidorphan Small molecule or natural product Approved drug Click here for species-specific activity table Hs Antagonist 10.3 pKi 172
⤷ pKi 10.3 (Ki 5.2x10-11 M) [172]
diprenorphine Small molecule or natural product Mm Antagonist 10.1 pKi 134
⤷ pKi 10.1 [134]
quadazocine Small molecule or natural product Click here for species-specific activity table Hs Antagonist 10.0 pKi 156
⤷ pKi 10.0 [156]
(-)-bremazocine Small molecule or natural product Click here for species-specific activity table Hs Antagonist 9.7 pKi 156
⤷ pKi 9.7 [156]
CTOP Peptide Hs Antagonist 9.7 pKi 134
⤷ pKi 9.7 [134]
nalmefene Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Antagonist 9.5 pKi 156
⤷ pKi 9.5 [156]
β-FNA Small molecule or natural product Click here for species-specific activity table Hs Antagonist 9.5 pKi 156
⤷ pKi 9.5 [156]
β-FNA Small molecule or natural product Mm Antagonist 9.5 pKi 134
⤷ pKi 9.5 [134]
NFP Small molecule or natural product Click here for species-specific activity table Hs Antagonist 9.4 pKi 182
⤷ pKi 9.4 (Ki 3.6x10-10 M) [182]
Description: In a competitive radioligand membrane binding assay measuring displacement of [3H]naloxone by NFP from μ receptor expressed in CHO cells.
naltrexone Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Antagonist 9.1 – 9.7 pKi 73,156
⤷ pKi 9.1 – 9.7 (Ki 7.1x10-10 – 1.99x10-10 M) [73,156]
GSK1521498 Small molecule or natural product Primary target of this compound Hs Antagonist 9.4 pKi 73
⤷ pKi 9.4 (Ki 4.17x10-10 M) [73]
alvimopan Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Ligand has a PDB structure Hs Antagonist 9.3 pKi 83
⤷ pKi 9.3 (Ki 4.7x10-10 M) [83]
diprenorphine Small molecule or natural product Click here for species-specific activity table Hs Antagonist 9.1 pKi 156
⤷ pKi 9.1 [156]
levallorphan Small molecule or natural product Approved drug Primary target of this compound Hs Antagonist 8.8 – 9.3 pKi 94
⤷ pKi 8.8 – 9.3 (Ki 1.69x10-9 – 4.8x10-10 M) [94]
Description: Competition binding assay- the calculated Ki varies depending on the radioligand used.
naloxone Small molecule or natural product Approved drug Click here for species-specific activity table Mm Antagonist 9.0 pKi 134
⤷ pKi 9.0 [134]
naldemedine Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Antagonist 8.9 pKi 67
⤷ pKi 8.9 (Ki 1.13x10-9 M) [67]
nalorphine Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Antagonist 8.9 pKi 156
⤷ pKi 8.9 [156]
naloxone Small molecule or natural product Approved drug Click here for species-specific activity table Hs Antagonist 8.9 pKi 156
⤷ pKi 8.9 [156]
BNTX Small molecule or natural product Click here for species-specific activity table Hs Antagonist 8.8 pKi 156
⤷ pKi 8.8 [156]
AT-076 Small molecule or natural product Click here for species-specific activity table Hs Antagonist 8.8 pKi 156,181
⤷ pKi 8.8 (Ki 1.67x10-9 M) [156,181]
Description: Radioligand binding assay
methylnaltrexone Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Antagonist 8.7 pKi 171
⤷ pKi 8.7 (Ki 2x10-9 M) [171]
Description: Displacement of [3H]DAMGO from human μ opioid receptors expressed in CHO cells
CTAP Peptide Click here for species-specific activity table Hs Antagonist 8.6 pKi 23,156
⤷ pKi 8.6 [23,156]
naloxone benzoylhydrazone Small molecule or natural product Click here for species-specific activity table Hs Antagonist 8.2 – 8.7 pKi 156
⤷ pKi 8.7 [156]
pKi 8.2 [156]
naltrindole Small molecule or natural product Click here for species-specific activity table Ligand has a PDB structure Hs Antagonist 8.2 pKi 156
⤷ pKi 8.2 [156]
naltriben Small molecule or natural product Click here for species-specific activity table Hs Antagonist 7.9 pKi 156
⤷ pKi 7.9 [156]
nor-binaltorphimine Small molecule or natural product Click here for species-specific activity table Hs Antagonist 7.7 pKi 156
⤷ pKi 7.7 [156]
LY2456302 Small molecule or natural product Click here for species-specific activity table Hs Antagonist 7.6 pKi 136
⤷ pKi 7.6 (Ki 2.4x10-8 M) [136]
zyklophin Peptide Click here for species-specific activity table Hs Antagonist 5.2 pKi 125
⤷ pKi 5.2 (Ki 5.88x10-6 M) [125]
NMRA-140 Small molecule or natural product Click here for species-specific activity table Hs Antagonist 7.0 pIC50 55
⤷ pIC50 7.0 (IC50 1.1x10-7 M) [55]
View species-specific antagonist tables
Antagonist Comments
β-FNA is an electrophilic affinity label. The pKi reflects both the reversible and irreversible binding components.
CTOP is a good somatostatin receptor (sst receptor) agonist in addition to having antagonist activity at μ opioid receptors; it should never be used in studies of μ receptor function in situations where sst receptors may be involved. CTAP does not activate sst receptors [31].

The μ receptor is tagged as the primary target for the drug levallorphan, since the drug is mainly used for its antagonistic actions as an antidote to opioid overdose. Note that this drug also acts as a partial agonist at the κ receptor.
Allosteric Modulators
Key to terms and symbols View all chemical structures Click column headers to sort
Ligand Sp. Action Value Parameter Reference
BMS-986123 Small molecule or natural product Hs Neutral 6.0 pKB 19
⤷ pKB 6.0 (KB 1x10-6 M) [19]
BMS-986121 Small molecule or natural product Hs Positive 5.7 pKB 19
⤷ pKB 5.7 (KB 2x10-6 M) [19]
BMS-986124 Small molecule or natural product Hs Neutral 5.7 pKB 19
⤷ pKB 5.7 (KB 2x10-6 M) [19]
BMS-986122 Small molecule or natural product Hs Positive 5.3 pKB 19
⤷ pKB 5.3 (KB 5x10-6 M) [19]
BMS-986187 Small molecule or natural product Rn Positive 7.2 pKi 91
⤷ pKi 7.2 (Ki 6.3x10-8 M) In the presence of 10 μM BMS-986187, the affinity of the μ-OR agonist DAMGO was enhanced 11-fold from 724 nM to 63 nM. [91]
BMS-986121 Small molecule or natural product Hs Positive 6.0 pEC50 19
⤷ pEC50 6.0 (EC50 1x10-6 M) [19]
BMS-986122 Small molecule or natural product Hs Positive 5.5 pEC50 19
⤷ pEC50 5.5 (EC50 3x10-6 M) [19]
View species-specific allosteric modulator tables
Allosteric Modulator Comments
BMS-986123 and BMS-986124 are Silent Allosteric Modulators (SAMs). These compounds neither potentiate nor inhibit the actions of an orthosteric agonist, however they block the actions of the Positive Allosteric Modulators (PAMs).
A number of proteins such as G protein-coupled receptor kinases, β-arrestins and G proteins clearly regulate μ opioid receptor affinities and function. In addition sodium and guanyl nucleotides can modify the functional μ receptor complex and G protein interaction. Also, μ receptors are reported to form heterodimers with other receptors of the OP family or with non-opioid G protein-coupled receptors. Heterodimerisation may alter μ receptor function and/or trafficking [49,53,126].
Other Binding Ligands
Key to terms and symbols Click column headers to sort
Ligand Sp. Action Value Parameter Reference
compound 16 [PMID: 31498617]