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κ receptor

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Target not currently curated in GtoImmuPdb

Target id: 318

Nomenclature: κ receptor

Family: Opioid receptors

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 7 380 8q11.23 OPRK1 opioid receptor kappa 1 64,102,134
Mouse 7 380 1 1.89 cM Oprk1 opioid receptor, kappa 1 8,47,60,76,127
Rat 7 380 5q12 Oprk1 opioid receptor, kappa 1 16,58,66-67,75
Previous and Unofficial Names Click here for help
KOR-1 | Kappa receptor | OP2 | KOP | KOPr
Database Links Click here for help
Specialist databases
GPCRDB oprk_human (Hs), oprk_mouse (Mm), oprk_rat (Rn)
Other databases
ChEMBL Target
DrugBank Target
Ensembl Gene
Entrez Gene
Human Protein Atlas
KEGG Gene
OMIM
Pharos
RefSeq Nucleotide
RefSeq Protein
SynPHARM
UniProtKB
Wikipedia
Selected 3D Structures Click here for help
Image of receptor 3D structure from RCSB PDB
Description:  Structure of the human kappa opioid receptor in complex with JDTic
PDB Id:  4DJH
Ligand:  JDTic
Resolution:  2.9Å
Species:  Human
References:  126
Image of receptor 3D structure from RCSB PDB
Description:  Structure of the Nanobody-Stabilized Active State of the Kappa Opioid Receptor
PDB Id:  6B73
Ligand:  MP1104
Resolution:  3.1Å
Species:  Human
References:  15
Natural/Endogenous Ligands Click here for help
big dynorphin {Sp: Human, Mouse, Rat}
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}
β-endorphin {Sp: Human} , β-endorphin {Sp: Mouse} , β-endorphin {Sp: Rat}
[Leu]enkephalin {Sp: Human, Mouse, Rat}
[Met]enkephalin {Sp: Human, Mouse, Rat}
α-neoendorphin {Sp: Human, Mouse, Rat}
β-neoendorphin {Sp: Human, Mouse, Rat}
Comments: Dynorphin A and big dynorphin are the highest potency endogenous ligands
Principal endogenous agonists (Human)
big dynorphin (PDYN, P01213), dynorphin A (PDYN, P01213)

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Agonists
Key to terms and symbols View all chemical structures Click column headers to sort
Ligand Sp. Action Value Parameter Reference
nalfurafine Small molecule or natural product Hs Full agonist 10.1 pKd 123
pKd 10.1 [123]
ethyketazocine Small molecule or natural product Hs Full agonist 9.4 pKd 135
pKd 9.4 [135]
enadoline Small molecule or natural product Hs Full agonist 8.6 – 9.2 pKd 35
pKd 8.6 – 9.2 [35]
[3H]U69593 Small molecule or natural product Ligand is labelled Ligand is radioactive Hs Full agonist 8.7 – 8.8 pKd 50,81,102
pKd 8.7 – 8.8 (Kd 2x10-9 – 1.6x10-9 M) [50,81,102]
(-)-bremazocine Small molecule or natural product Click here for species-specific activity table Hs Partial agonist 10.5 pKi 115
pKi 10.5 [115]
dynorphin A {Sp: Human, Mouse, Rat} Peptide Ligand is endogenous in the given species Rn Full agonist 10.0 – 10.3 pKi 58,66
pKi 10.0 – 10.3 [58,66]
ethylketocyclazocine Small molecule or natural product Click here for species-specific activity table Hs Full agonist 10.0 pKi 115
pKi 10.0 [115]
(-)-cyclazocine Small molecule or natural product Click here for species-specific activity table Hs Partial agonist 10.0 pKi 115
pKi 10.0 [115]
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 9.3 – 10.7 pKi 81,115
pKi 9.3 – 10.7 [81,115]
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 24
pKi 9.9 (Ki 1.2x10-10 M) [24]
Description: Displacement of [3H]U69593 from human κ opioid receptor expressed in CHO cells.
dynorphin A-(1-13) {Sp: Human, Mouse, Rat} Peptide Ligand is endogenous in the given species Rn Full agonist 9.9 pKi 66
pKi 9.9 [66]
dynorphin-(1-11) Peptide Click here for species-specific activity table Hs Full agonist 9.7 pKi 115
pKi 9.7 [115]
etorphine Small molecule or natural product Click here for species-specific activity table Hs Full agonist 9.7 pKi 115
pKi 9.7 [115]
GR 89696 Small molecule or natural product Hs Full agonist 9.7 pKi 88
pKi 9.7 [88]
enadoline Small molecule or natural product Hs Full agonist 9.6 pKi 40,73
pKi 9.6 [40,73]
probe 1.1 [PMID: 24187130] Small molecule or natural product Hs Agonist 9.6 pKi 133
pKi 9.6 (Ki 2.5x10-10 M) [133]
dynorphin A {Sp: Human, Mouse, Rat} Peptide Click here for species-specific activity table Ligand is endogenous in the given species Hs Full agonist 8.3 – 10.8 pKi 81,102,115,134-135
pKi 8.3 – 10.8 [81,102,115,134-135]
dynorphin B {Sp: Human, Mouse, Rat} Peptide Ligand is endogenous in the given species Rn Full agonist 9.5 pKi 66
pKi 9.5 [66]
U69593 Small molecule or natural product Hs Full agonist 9.5 pKi 50,115
pKi 9.5 [50,115]
naloxone benzoylhydrazone Small molecule or natural product Click here for species-specific activity table Hs Partial agonist 9.5 pKi 115
pKi 9.5 [115]
MP1104 Small molecule or natural product Hs Agonist 9.5 pKi 15
pKi 9.5 (Ki 3.3x10-10 M) [15]
probe 2.1 [PMID: 24187130] Small molecule or natural product Hs Agonist 9.5 pKi 133
pKi 9.5 (Ki 3.5x10-10 M) [133]
α-neoendorphin {Sp: Human, Mouse, Rat} Peptide Ligand is endogenous in the given species Rn Full agonist 8.9 – 10.0 pKi 58,66
pKi 8.9 – 10.0 [58,66]
HS665 Small molecule or natural product Primary target of this compound Click here for species-specific activity table Hs Full agonist 9.3 pKi 107
pKi 9.3 (Ki 4.9x10-10 M) [107]
α-neoendorphin {Sp: Human, Mouse, Rat} Peptide Ligand is endogenous in the given species Hs Full agonist 8.3 – 10.2 pKi 102,134
pKi 8.3 – 10.2 [102,134]
β-neoendorphin {Sp: Human, Mouse, Rat} Peptide Ligand is endogenous in the given species Rn Full agonist 9.1 pKi 66
pKi 9.1 [66]
E2078 Peptide Hs Full agonist 9.1 pKi 89
pKi 9.1 [89]
dynorphin B {Sp: Human, Mouse, Rat} Peptide Click here for species-specific activity table Ligand is endogenous in the given species Hs Partial agonist 8.1 – 9.9 pKi 81,102,115
pKi 8.1 – 9.9 [81,102,115]
spiradoline Small molecule or natural product Rn Full agonist 9.0 pKi 16
pKi 9.0 [16]
asimadoline Small molecule or natural product Immunopharmacology Ligand Cp Agonist 9.0 pKi 30
pKi 9.0 (Ki 1x10-9 M) [30]
Description: Displacement of [3H]- 69593 from K opioid receptors from guinea pig cerebellum.
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 8.0 – 9.9 pKi 81,102,115,128
pKi 8.0 – 9.9 [81,102,115,128]
ethyketazocine Small molecule or natural product Rn Full agonist 8.8 pKi 66
pKi 8.8 [66]
E2078 Peptide Rn Full agonist 8.8 pKi 66
pKi 8.8 [66]
ICI 204448 Small molecule or natural product Rn Full agonist 8.8 pKi 16
pKi 8.8 [16]
tifluadom Small molecule or natural product Hs Full agonist 8.8 pKi 135
pKi 8.8 [135]
U50488 Small molecule or natural product Hs Agonist 7.8 – 9.7 pKi 14,81,102,115,122,134-135
pKi 7.8 – 9.7 [14,81,102,115,122,134-135]
cebranopadol Small molecule or natural product Click here for species-specific activity table Hs Agonist 8.6 pKi 59
pKi 8.6 (Ki 2.6x10-9 M) [59]
Description: Radioligand binding assay
hydromorphone Small molecule or natural product Approved drug Click here for species-specific activity table Hs Agonist 8.6 pKi 124
pKi 8.6 (Ki 2.8x10-9 M) [124]
nalorphine Small molecule or natural product Approved drug Click here for species-specific activity table Hs Partial agonist 7.9 – 9.1 pKi 115,135
pKi 7.9 – 9.1 [115,135]
U50488 Small molecule or natural product Rn Partial agonist 8.2 – 8.7 pKi 16,58,66
pKi 8.2 – 8.7 [16,58,66]
U69593 Small molecule or natural product Rn Full agonist 8.0 – 8.7 pKi 16,66
pKi 8.0 – 8.7 [16,66]
salvinorin A Small molecule or natural product Hs Full agonist 7.8 – 8.7 pKi 11,93
pKi 7.8 – 8.7 [11,93]
BU08028 Small molecule or natural product Click here for species-specific activity table Hs Agonist 8.3 pKi 44
pKi 8.3 (Ki 5.63x10-9 M) [44]
compound 3 [PMID: 23134120] Small molecule or natural product Click here for species-specific activity table Hs Partial agonist 8.2 pKi 107
pKi 8.2 (Ki 5.9x10-9 M) [107]
(-)-pentazocine Small molecule or natural product Approved drug Click here for species-specific activity table Hs Partial agonist 7.8 – 8.6 pKi 115,135
pKi 7.8 – 8.6 [115,135]
β-neoendorphin {Sp: Human, Mouse, Rat} Peptide Ligand is endogenous in the given species Hs Full agonist 7.9 pKi 102
pKi 7.9 [102]
tramadol Small molecule or natural product Approved drug Click here for species-specific activity table Hs Agonist 7.8 pKi 124
pKi 7.8 (Ki 1.4x10-8 M) [124]
Description: Displacement of the kappa agonist U69593 from the kappa receptor expressed in CHO cells.
normorphine Small molecule or natural product Click here for species-specific activity table Hs Full agonist 7.8 pKi 115
pKi 7.8 [115]
ADL5747 Small molecule or natural product Click here for species-specific activity table Hs Agonist 7.6 pKi 55
pKi 7.6 (Ki 2.5x10-8 M) [55]
BW373U86 Small molecule or natural product Click here for species-specific activity table Rn Agonist 7.5 pKi 12
pKi 7.5 (Ki 3.4x10-8 M) [12]
nalbuphine Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Full agonist 7.4 – 7.5 pKi 135
pKi 7.4 – 7.5 [135]
ADL5859 Small molecule or natural product Click here for species-specific activity table Hs Agonist 7.4 pKi 54
pKi 7.4 (Ki 3.7x10-8 M) [54]
carfentanil Small molecule or natural product Click here for species-specific activity table Cp Agonist 7.4 pKi 17
pKi 7.4 (Ki 4.31x10-8 M) [17]
Description: Binding affinity- displacement of [3H]U69593 in guinea pig whole brain
morphine Small molecule or natural product Approved drug Click here for species-specific activity table Ligand has a PDB structure Hs Partial agonist 7.3 pKi 115
pKi 7.3 [115]
cebranopadol Small molecule or natural product Click here for species-specific activity table Rn Agonist 7.2 pKi 59
pKi 7.2 (Ki 6.4x10-8 M) [59]
Description: Radioligand binding assay
β-endorphin {Sp: Human} Peptide Click here for species-specific activity table Ligand is endogenous in the given species Hs Partial agonist 6.3 – 7.9 pKi 102,115
pKi 6.3 – 7.9 [102,115]
dihydromorphine Small molecule or natural product Click here for species-specific activity table Hs Partial agonist 7.1 pKi 115
pKi 7.1 [115]
fentanyl Small molecule or natural product Approved drug Click here for species-specific activity table Ligand has a PDB structure Hs Partial agonist 7.1 pKi 115
pKi 7.1 [115]
etonitazene Small molecule or natural product Click here for species-specific activity table Hs Partial agonist 6.9 pKi 115
pKi 6.9 [115]
BW373U86 Small molecule or natural product Click here for species-specific activity table Hs Agonist 6.9 pKi 54
pKi 6.9 (Ki 1.3x10-7 M) [54]
SCH221510 Small molecule or natural product Click here for species-specific activity table Hs Agonist 6.9 pKi 120
pKi 6.9 (Ki 1.31x10-7 M) [120]
Description: Radioligand binding assay
morphine Small molecule or natural product Approved drug Click here for species-specific activity table Ligand has a PDB structure Rn Partial agonist 6.7 – 7.0 pKi 16,66
pKi 6.7 – 7.0 [16,66]
β-endorphin {Sp: Human} Peptide Click here for species-specific activity table Rn Full agonist 6.8 pKi 66
pKi 6.8 [66]
UFP-512 Small molecule or natural product Click here for species-specific activity table Hs Agonist 6.7 pKi 121
pKi 6.7 [121]
Description: Measuring displacement of [3H]-diprenorphine in vitro
hydrocodone Small molecule or natural product Approved drug Click here for species-specific activity table Hs Agonist 6.6 pKi 74
pKi 6.6 (Ki 2.6x10-7 M) [74]
(-)-methadone Small molecule or natural product Click here for species-specific activity table Hs Partial agonist 6.5 pKi 115
pKi 6.5 [115]
DAMGO Peptide Click here for species-specific activity table Hs Partial agonist 6.5 pKi 115
pKi 6.5 [115]
SR16835 Small molecule or natural product Click here for species-specific activity table Hs Agonist 6.2 pKi 116
pKi 6.2 (Ki 6.813x10-7 M) [116]
Description: Radioligand binding assay
bilorphin Small molecule or natural product Click here for species-specific activity table Hs Agonist 6.1 pKi 21
pKi 6.1 (Ki 7.7x10-7 M) [21]
[Leu]enkephalin {Sp: Human, Mouse, Rat} Peptide Ligand is endogenous in the given species Rn Full agonist 6.0 pKi 66
pKi 6.0 [66]
[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 6.0 pKi 66
pKi 6.0 [66]
DAMGO Peptide Click here for species-specific activity table Rn Partial agonist 5.9 pKi 66
pKi 5.9 [66]
difelikefalin Peptide Immunopharmacology Ligand Mm Agonist 10.3 pEC50 98
pEC50 10.3 (EC50 4.8x10-11 M) [98]
difelikefalin Peptide Primary target of this compound Immunopharmacology Ligand Hs Agonist 9.8 pEC50 98
pEC50 9.8 (EC50 1.6x10-10 M) [98]
HS665 Small molecule or natural product Primary target of this compound Click here for species-specific activity table Hs Full agonist 8.4 pEC50 107
pEC50 8.4 (EC50 3.62x10-9 M) [107]
Description: Measuring stimulation of [35S]GTPγS binding.
compound 3 [PMID: 23134120] Small molecule or natural product Click here for species-specific activity table Hs Partial agonist 7.5 pEC50 107
pEC50 7.5 (EC50 3.5x10-8 M) [107]
Description: Measuring stimulation of [35S]GTPγS binding.
probe 1.1 [PMID: 24187130] Small molecule or natural product Hs Biased agonist 5.4 – 7.5 pEC50 133
pEC50 7.5 (EC50 3.1x10-8 M) [133]
Description: Measuring [35S]GTPγS binding
pEC50 5.4 (EC50 4.129x10-6 M) [133]
Description: Measuring βarrestin2 recruitment
probe 2.1 [PMID: 24187130] Small molecule or natural product Hs Biased agonist 5.0 – 7.1 pEC50 133
pEC50 7.1 (EC50 8.47x10-8 M) [133]
Description: Measuring [35S]GTPγS binding
pEC50 <5.0 (EC50 >1x10-5 M) [133]
Description: Measuring βarrestin2 recruitment
α-neoendorphin {Sp: Human, Mouse, Rat} Peptide Click here for species-specific activity table Ligand is endogenous in the given species Mm Full agonist 10.0 pIC50 127
pIC50 10.0 [127]
dynorphin B {Sp: Human, Mouse, Rat} Peptide Ligand is endogenous in the given species Mm Full agonist 10.0 pIC50 127
pIC50 10.0 [127]
dynorphin A-(1-8) {Sp: Human, Mouse, Rat} Peptide Ligand is endogenous in the given species Mm Full agonist 9.7 pIC50 127
pIC50 9.7 [127]
[D-Ala2,F5,Phe4]dynorphin-(1-17)-NH2 Peptide Mm Full agonist 9.7 pIC50 127
pIC50 9.7 [127]
dynorphin-(1-17)-NH2 Peptide Mm Full agonist 9.7 pIC50 127
pIC50 9.7 [127]
(-)-bremazocine Small molecule or natural product Mm Full agonist 9.5 pIC50 127
pIC50 9.5 [127]
dynorphin A {Sp: Human, Mouse, Rat} Peptide Ligand is endogenous in the given species Mm Full agonist 9.4 pIC50 127
pIC50 9.4 [127]
[Met5]dynorphin-(1-17) Peptide Mm Full agonist 9.2 pIC50 127
pIC50 9.2 [127]
ethyketazocine Small molecule or natural product Click here for species-specific activity table Mm Full agonist 9.0 pIC50 127
pIC50 9.0 [127]
U50488 Small molecule or natural product Mm Partial agonist 9.0 pIC50 127
pIC50 9.0 [127]
spiradoline Small molecule or natural product Mm Full agonist 9.0 pIC50 127
pIC50 9.0 [127]
U69593 Small molecule or natural product Mm Full agonist 8.6 pIC50 127
pIC50 8.6 [127]
ICI 204448 Small molecule or natural product Mm Full agonist 8.2 pIC50 127
pIC50 8.2 [127]
[D-Ala2,F5,Phe4]dynorphin-(1-13)-NH2 Peptide Mm Full agonist 7.7 pIC50 127
pIC50 7.7 [127]
β-endorphin {Sp: Human} Peptide Click here for species-specific activity table Mm Partial agonist 7.4 pIC50 127
pIC50 7.4 [127]
nalbuphine Small molecule or natural product Approved drug Mm Full agonist 7.4 pIC50 127
pIC50 7.4 [127]
pethidine Small molecule or natural product Approved drug Click here for species-specific activity table Hs Agonist 5.6 pIC50 86
pIC50 5.6 (IC50 2.37x10-6 M) [86]
AR-M1000390 Small molecule or natural product Click here for species-specific activity table Hs Agonist 5.1 pIC50 4
pIC50 5.1 (IC50 7.47x10-6 M) [4]
[3H]enadoline Small molecule or natural product Ligand is labelled Ligand is radioactive Hs Full agonist - - 103
[103]
View species-specific agonist tables
Agonist Comments
Ki values were determined in the absence of Na+ and GDP, except TRK820.

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 GTPγS binding in cell lines expressing cloned human kappa receptors. Agents giving 85% or greater stimulation than that given by U69593 have been characterized as Full Agonists [115].

κ opioid receptors have been divided into several different subtypes, mainly on the basis of [3H]agonist binding assays. Generally 2 subtypes are recognised: κ1 and κ2. The benzeneacetamides and peptides are considered κ1 agonists and the benzomorphans bind to κ1 and κ2. However, there is only one gene product and the subtypes are considered putative.

Selective κ agonists are of several structural types. All have high affinity for the κ receptor and are full agonists.

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 [74]. Similarly, we have tagged the μ receptor as the primary target of the drug hydromorphone [124].
Antagonists
Key to terms and symbols View all chemical structures Click column headers to sort
Ligand Sp. Action Value Parameter Reference
LY2456302 Small molecule or natural product Primary target of this compound Click here for species-specific activity table Hs Antagonist 9.1 pKB 92
pKB 9.1 (KB 8.13x10-10 M) [92]
Description: Measuring inhibition of agonist-induced [35S]GTPγS binding in vitro.
zyklophin Peptide Primary target of this compound Click here for species-specific activity table Hs Antagonist 7.1 pKB 80
pKB 7.1 (KB 8.39x10-8 M) [80]
Description: Schild analysis of zyklophin vs. Dynorphin A-(1-13)NH2
[3H]diprenorphine Small molecule or natural product Click here for species-specific activity table Ligand is labelled Ligand is radioactive Hs Antagonist 9.1 pKd 3,102
pKd 9.1 (Kd 7.94x10-10 M) [3,102]
nor-binaltorphimine Small molecule or natural product Rn Antagonist 9.6 – 10.7 pKi 16,58,66
pKi 9.6 – 10.7 [16,58,66]
JDTic Small molecule or natural product Primary target of this compound Ligand has a PDB structure Hs Antagonist 9.0 – 11.2 pKi 70,113,130
pKi 11.2 (Ki 6x10-12 M) [113]
Description: Measuring antagonism of U50,488-induced [35S]GTPγS binding
pKi 9.0 – 9.4 (Ki 1x10-9 – 3.98x10-10 M) [70,113,130]
nor-binaltorphimine Small molecule or natural product Click here for species-specific activity table Hs Antagonist 8.9 – 11.0 pKi 81,85,102,115,134-135
pKi 8.9 – 11.0 [81,85,102,115,134-135]
5'-guanidinonaltrindole Small molecule or natural product Hs Antagonist 9.7 – 9.9 pKi 41,81,109
pKi 9.7 – 9.9 [41,81,109]
β-FNA Small molecule or natural product Click here for species-specific activity table Hs Antagonist 9.7 pKi 115
pKi 9.7 [115]
quadazocine Small molecule or natural product Click here for species-specific activity table Hs Antagonist 9.7 pKi 115
pKi 9.7 [115]
diprenorphine Small molecule or natural product Click here for species-specific activity table Hs Antagonist 9.6 – 9.7 pKi 81,115,134-135
pKi 9.6 – 9.7 [81,115,134-135]
buprenorphine Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Antagonist 9.1 – 10.2 pKi 115,135
pKi 9.1 – 10.2 [115,135]
samidorphan Small molecule or natural product Click here for species-specific activity table Hs Antagonist 9.6 pKi 125
pKi 9.6 (Ki 2.3x10-10 M) [125]
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 115
pKi 9.5 [115]
LY2456302 Small molecule or natural product Primary target of this compound Click here for species-specific activity table Hs Antagonist 9.1 pKi 92
pKi 9.1 (Ki 8.07x10-10 M) [92]
AT-076 Small molecule or natural product Click here for species-specific activity table Hs Antagonist 8.9 pKi 115,130
pKi 8.9 (Ki 1.14x10-9 M) [115,130]
Description: Radioligand binding assay
naltrexone Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Antagonist 8.4 – 9.4 pKi 81,102,115
pKi 8.4 – 9.4 [81,102,115]
BNTX Small molecule or natural product Click here for species-specific activity table Hs Antagonist 8.4 pKi 115
pKi 8.4 [115]
naltriben Small molecule or natural product Click here for species-specific activity table Hs Antagonist 8.4 pKi 115
pKi 8.4 [115]
NFP Small molecule or natural product Click here for species-specific activity table Hs Antagonist 8.3 pKi 132
pKi 8.3 (Ki 4.8x10-9 M) [132]
Description: In a competitive radioligand membrane binding assay measuring displacement of [3H]diprenorphine by NFP from κ receptor expressed in CHO cells.
methylnaltrexone Small molecule or natural product Approved drug Click here for species-specific activity table Hs Antagonist 8.2 pKi 124
pKi 8.2 (Ki 6.3x10-9 M) [124]
naloxone Small molecule or natural product Approved drug Primary target of this compound Click here for species-specific activity table Hs Antagonist 7.6 – 8.6 pKi 81,102,115,134-135
pKi 7.6 – 8.6 [81,102,