Opioid receptor

opioid receptorsopioidopiate receptoropiate receptorsopioid-receptor agonistreceptors, opioidε-opioid receptorμ-opioidμ-opioid receptor
Opioid receptors are a group of inhibitory G protein-coupled receptors with opioids as ligands.wikipedia
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Opioid

opioidsopioid analgesicendogenous opioids
Opioid receptors are a group of inhibitory G protein-coupled receptors with opioids as ligands.
Opioids are substances that act on opioid receptors to produce morphine-like effects.

Enkephalin

enkephalins[ D -Ala 2 , D -Leu 5 ]enkephalinenkephaline
The endogenous opioids are dynorphins, enkephalins, endorphins, endomorphins and nociceptin.
The enkephalins are termed endogenous ligands, as they are internally derived and bind to the body's opioid receptors.

Opiate

opiatesOpiate pathwayopioid
By the mid-1960s, it had become apparent from pharmacologic studies that opiate drugs were likely to exert their actions at specific receptor sites, and that there were likely to be multiple such sites.
Opioid, a more modern term, is used to designate all substances, both natural and synthetic, that bind to opioid receptors in the brain (including antagonists).

Μ-opioid receptor

μ-opioidmu opioid receptorμ-
In 1973, Candace Pert and Solomon H. Snyder published the first detailed binding study of what would turn out to be the μ opioid receptor, using 3 H-naloxone.
The μ-opioid receptors (MOR) are a class of opioid receptors with a high affinity for enkephalins and beta-endorphin, but a low affinity for dynorphins.

Δ-opioid receptor

DORδ-opioiddelta opioid receptor
The δ-opioid receptor, also known as delta opioid receptor or simply delta receptor, abbreviated DOR, is an inhibitory 7-transmembrane G-protein coupled receptor coupled to the G protein G i /G 0 and has enkephalins as its endogenous ligands.

Candace Pert

Candace B. Pert
In 1973, Candace Pert and Solomon H. Snyder published the first detailed binding study of what would turn out to be the μ opioid receptor, using 3 H-naloxone.
Candace Beebe Pert (June 26, 1946 – September 12, 2013) was an American neuroscientist and pharmacologist who discovered the opiate receptor, the cellular binding site for endorphins in the brain.

Solomon H. Snyder

Sol SnyderSolomon Snyder
In 1973, Candace Pert and Solomon H. Snyder published the first detailed binding study of what would turn out to be the μ opioid receptor, using 3 H-naloxone.
He is most famous for his research on the opioid receptor, for which he received the Albert Lasker Award for Basic Medical Research in 1978.

Κ-opioid receptor

κ-opioidKORkappa opioid receptor
The KOR is a type of opioid receptor that binds the opioid peptide dynorphin as the primary endogenous ligand (substrate naturally occurring in the body).

Analgesic

analgesiaanalgesicspainkillers
Activation of this receptor produces strong analgesia and release of met-enkephalin; a number of widely used opioid agonists, such as the μ agonist etorphine and the κ agonist bremazocine, have been shown to act as agonists for this effect (even in the presence of antagonists to their more well known targets), while buprenorphine has been shown to act as an epsilon antagonist.
Morphine, the archetypal opioid, and other opioids (e.g., codeine, oxycodone, hydrocodone, dihydromorphine, pethidine) all exert a similar influence on the cerebral opioid receptor system.

Periaqueductal gray

periaqueductal greyperiaqueductal gray mattercentral gray
They are also located in high concentrations in the Periaqueductal gray, Locus coeruleus, and the Rostral ventromedial medulla.
Three known kinds of opioid receptors have been identified: mu, kappa and delta .

OGFr

opioid growth factor receptorzeta (
This receptor is now most commonly referred to as the opioid growth factor receptor (OGFr).
The endogenous ligand is thus a known opioid peptide, and OGFr was originally discovered and named as a new opioid receptor zeta .

Opioid peptide

endogenous opioidopioid peptidesopioid
However, σ receptors were found to not be activated by endogenous opioid peptides, and are quite different from the other opioid receptors in both function and gene sequence, so they are now not usually classified with the opioid receptors.
Opioid peptides are peptides that bind to opioid receptors in the brain; opiates and opioids mimic the effect of these peptides.

Receptor antagonist

antagonistantagonistscompetitive antagonist
The first attempt to purify the receptor involved the use of a novel opioid receptor antagonist called chlornaltrexamine that was demonstrated to bind to the opioid receptor.
Buprenorphine, a partial agonist of the μ-opioid receptor, binds with weak morphine-like activity and is used clinically as an analgesic in pain management and as an alternative to methadone in the treatment of opioid dependence.

Morphine

morphiamorphine addictionmorphine sulfate
Social attachment was demonstrated to be mediated by the opioid system through experiments administering morphine and naltrexone, an opioid agonist and antagonist, to juvenile guinea pigs.
Heroin is converted to morphine before binding to the opioid receptors in the brain and spinal cord, where morphine causes the subjective effects, which is what the addicted individuals are seeking.

Sigma receptor

sigmaσσ receptor
Sigma receptors were once considered to be opioid receptors due to the antitussive actions of many opioid drugs' being mediated via σ receptors, and the first selective σ agonists being derivatives of opioid drugs (e.g., allylnormetazocine).
σ–receptors were once thought to be a type of opioid receptor.

Ketazocine

k'''''etocyclazocine
In similar manner, a drug known as ketocyclazocine was first shown to attach itself to "κ" (kappa) receptors, while the "δ" (delta) receptor was named after the mouse vas deferens tissue in which the receptor was first characterised.
Ketazocine (INN), also known as ketocyclazocine, is a benzomorphan derivative used in opioid receptor research.

Naltrexone

naltrexone hydrochlorideNaltrexone (1967)Vivitrex
Social attachment was demonstrated to be mediated by the opioid system through experiments administering morphine and naltrexone, an opioid agonist and antagonist, to juvenile guinea pigs.
The blockade of opioid receptors is the basis behind naltrexone's action in the management of opioid dependence—it reversibly blocks or attenuates the effects of opioids.

Buprenorphine

SuboxonesubutexBuprenorphrine
Activation of this receptor produces strong analgesia and release of met-enkephalin; a number of widely used opioid agonists, such as the μ agonist etorphine and the κ agonist bremazocine, have been shown to act as agonists for this effect (even in the presence of antagonists to their more well known targets), while buprenorphine has been shown to act as an epsilon antagonist.
Buprenorphine affects different types of opioid receptors in different ways.

Opioid antagonist

narcotic antagonistantagonistEndorphin blocker
Opioid antagonist
An opioid antagonist, or opioid receptor antagonist, is a receptor antagonist that acts on one or more of the opioid receptors.

Alazocine

(+)-Alazocine(−)-Alazocineallylnormetazocine
Sigma receptors were once considered to be opioid receptors due to the antitussive actions of many opioid drugs' being mediated via σ receptors, and the first selective σ agonists being derivatives of opioid drugs (e.g., allylnormetazocine).
Conversely, the -stereoisomer has little affinity for the opioid receptors (K i for 1,900 nM, 1,600 nM, and 19,000 nM for the μ-, κ-, δ-opioid receptors in guinea pig brain membranes) and instead is a selective and high-affinity agonist of the σ 1 receptor (K i = 48–66 nM in guinea pig brain membranes).

Beta-Endorphin

β-endorphinbeta''-endorphinbeta(β)-endorphins
The existence of this receptor was suspected after the endogenous opioid peptide beta-endorphin was shown to produce additional actions that did not seem to be mediated through any of the known opioid receptors.
β-Endorphin is an agonist of the opioid receptors; it preferentially binds to the μ-opioid receptor.

G protein-coupled inwardly-rectifying potassium channel

GIRKsg protein-coupled inwardly-rectifying potassium channelsG-protein-regulated inwardly rectifying K + channels
Embedded in the cell membrane is also the G protein-coupled inwardly-rectifying potassium channel.
A wide variety of G protein-coupled receptors activate GIRKs, including the M 2 -muscarinic, A 1 -adenosine, α 2 -adrenergic, D 2 -dopamine, μ- δ-, and κ-opioid, 5-HT 1A serotonin, somatostatin, galanin, m-Glu, GABA B, TAAR1, CB 1 and CB 2, and sphingosine-1-phosphate receptors.

Post-translational modification

posttranslational modificationpost-translational modificationspost-translational
Research has so far failed to identify the genetic evidence of the subtypes, and it is thought that they arise from post-translational modification of cloned receptor types.
The nociceptin/nociceptin opioid receptor system is involved in the reinforcing or conditioning effects of alcohol.

Cell surface receptor

transmembrane receptorreceptorcell surface receptors
Opioid receptors are a group of inhibitory G protein-coupled receptors with opioids as ligands.

Ligand (biochemistry)

affinityligandbinding affinity
Opioid receptors are a group of inhibitory G protein-coupled receptors with opioids as ligands.