Opioid receptor

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This editable Main Article is under development and subject to a disclaimer.

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Opioid receptors are "cell membrane proteins that bind opioids and trigger intracellular changes which influence the behavior of cells. The endogenous ligands for opioid receptors in mammals include three families of peptides, the enkephalins, endorphins, and dynorphins. The receptor classes include mu, delta, and kappa receptors. Sigma receptors bind several psychoactive substances, including certain opioids, but their endogenous ligands are not known."[1]

Opioid analgesics stimulate opioid receptors.

## Contents

* 1 Classification
* 1.1 kappa receptor
* 1.2 mu receptor
* 1.3 delta receptor
* 2 References

## Classification[edit]

Opioid receptors[2][3] Receptor | Functions

|

Delta | Analgesia,
Kappa | Analgesia, inhibition of gastrointestinal motility, psychotropic effect
Mu | Analgesia, inhibition of gastrointestinal motility, inhibition of respiration, sedation and physical dependency

There a several cell surface receptors for opioids. All are G-protein-coupled receptors.

### kappa receptor[edit]

Kappa receptors are a "class of opioid receptors recognized by its pharmacological profile. Kappa opioid receptors bind dynorphins with a higher affinity than endorphins which are themselves preferred to enkephalins."[4]

### mu receptor[edit]

Mu receptors are a "class of opioid receptors recognized by its pharmacological profile. Mu opioid receptors bind, in decreasing order of affinity, endorphins, dynorphins, met-enkephalin, and leu-enkephalin. They have also been shown to be molecular receptors for morphine."[5]

Alvimopan is a selective mu receptor antagonist used for treatment of postoperative ileus after bowel resection.[6] Methylnaltrexone, is approved by the United States of America Food and Drug Administration for the treatment of constipation due to opioid analgesics, is another example of a mu receptor antagonist.[7]

### delta receptor[edit]

Delta receptors are a "class of opioid receptors recognized by its pharmacological profile. Delta opioid receptors bind endorphins and enkephalins with approximately equal affinity and have less affinity for dynorphins."[8]

## References[edit]

1. ↑ Anonymous (2025), Opioid receptor (English). Medical Subject Headings. U.S. National Library of Medicine.
2. ↑ Gutstein Howard B, Akil Huda, "Chapter 21. Opioid Analgesics" (Chapter). Brunton LL, Lazo JS, Parker KL: Goodman & Gilman's The Pharmacological Basis of Therapeutics, 11th ed.
3. ↑ Masters, Susan B.; Katzung, Bertram G.; Trevor, Anthony J. (2009). “Basic Pharmacology of the Opioid Analgesics”, Basic and Clinical Pharmacology, 11th. New York: McGraw-Hill Medical. ISBN 0-07-160405-7.
4. ↑ Anonymous (2025), kappa receptor (English). Medical Subject Headings. U.S. National Library of Medicine.
5. ↑ Anonymous (2025), mu receptor (English). Medical Subject Headings. U.S. National Library of Medicine.
6. ↑ Anonymous (December 2008). "Alvimopan (Entereg) for Postoperative Ileus". Medical Letter 50 (1300): 93. [e]
7. ↑ Thomas J, Karver S, Cooney GA, et al (May 2008). "Methylnaltrexone for opioid-induced constipation in advanced illness". N. Engl. J. Med. 358 (22): 2332–43. DOI:10.1056/NEJMoa0707377. PMID 18509120. Research Blogging.
8. ↑ Anonymous (2025), delta receptor (English). Medical Subject Headings. U.S. National Library of Medicine.