Morphiceptin is a

tetrapeptide A tetrapeptide is a peptide, classified as an oligopeptide, since it only consists of four amino acids joined by peptide bonds. Many tetrapeptides are pharmacologically active, often showing affinity and specificity for a variety of receptors in p ...

(Tyr-Pro-Phe-Pro-NH₂) that is a selective

μ-opioid receptor 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. They are also referred to as μ(''mu'')-opioid peptide (MOP) receptors. The prototypical � ...

agonist An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the ago ...

. It is derived from β-casomorphin and has over 1,000 times selectivity for μ- over δ-opioid receptors. When injected intracerebroventricularly (into the ventricular system of the brain), morphiceptin had an

analgesic An analgesic drug, also called simply an analgesic (American English), analgaesic (British English), pain reliever, or painkiller, is any member of the group of drugs used to achieve relief from pain (that is, analgesia or pain management). It ...

ED₅₀ of 1.7 nmol per animal. The analgesic effects of morphiceptin were reversed by

naloxone Naloxone, sold under the brand names Narcan (4 mg) and Kloxxado (8 mg) among others, is a medication used to reverse or reduce the effects of opioids. It is commonly used to counter decreased breathing in opioid overdose. Effects begin within ...

, meaning that the analgesic effect is mediated by the μ-opioid receptor. Morphiceptin is the (1S,2S,3S,4S)-form whereas deproceptin is the (1S,2S,3S,4R)-form 4799-23-5

References

{{Opioidergics Analgesics Opioid peptides Tetrapeptides

See also

References