Mu-opioid receptor

The mu-opioid receptor is a G-protein-coupled receptor activated by endogenous opioid peptides and opioid drugs. Its signaling mediates analgesia, reward, respiratory depression, and reduced gut motility.

Gi/o protein: A family of heterotrimeric G proteins that inhibits adenylyl cyclase and regulates ion channels. The receptor couples mainly to Gi/o proteins, reducing neuronal excitability through several downstream pathways.
Opioid peptide: A peptide that binds opioid receptors and can reduce pain or alter other neural functions. Endogenous opioid peptides activate this receptor as part of the body's own signaling system.
Opioid analgesic: A drug that reduces pain by activating opioid receptors or otherwise modulating opioid signaling. Many opioid analgesics relieve pain largely through activation of mu receptors.
Analgesia: The reduction or absence of pain sensation without necessarily causing loss of consciousness. Mu receptors suppress pain signaling in spinal and brain pathways, producing opioid analgesia.
OPRM1: The human gene that encodes the mu-opioid receptor. Genetic variation and alternative splicing of OPRM1 may help explain differences in opioid responses.
Adenylyl cyclase: An enzyme that converts ATP into cyclic AMP, a widely used intracellular signaling molecule. Mu-receptor signaling inhibits this enzyme, lowering cyclic AMP in responsive cells.
Beta-endorphin: An endogenous opioid peptide produced from proopiomelanocortin that can activate opioid receptors. It is a potent natural ligand that activates mu receptors in several tissues.
Morphine: A naturally occurring opiate alkaloid used as an analgesic and the reference drug for opioid potency. Morphine produces much of its analgesia and other characteristic effects through mu-receptor activation.
Mesolimbic pathway: A dopamine pathway connecting midbrain regions, especially the ventral tegmental area, with limbic structures. Mu-receptor activity can increase dopamine signaling in this circuit, contributing to opioid reward.
Alternative splicing: RNA processing that produces different mature transcripts from the same gene by selecting distinct exon combinations. OPRM1 splice variants may encode receptor forms with differing properties and pharmacological responses.

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