Opioid receptor

Opioid receptors are G-protein-coupled receptors activated by endogenous opioid peptides and opioid drugs. They regulate pain, reward, mood, and other processes by changing cellular signaling.

G protein-coupled receptor: A cell-surface receptor that activates intracellular G proteins in response to extracellular signals. Opioid receptors belong to this large receptor family and use its signaling framework.
Mu-opioid receptor: An opioid receptor subtype encoded by OPRM1 and activated by endogenous peptides and opioid drugs. It mediates many opioid effects, including analgesia, euphoria, and respiratory depression.
Opioid analgesic: A drug that relieves pain through activation of opioid receptors. These medicines exploit receptor signaling to reduce pain transmission and perception.
Opioid tolerance: A diminished response to opioids after repeated exposure, often requiring higher doses for the same effect. Receptor regulation and downstream adaptation help explain declining drug effects over time.
Opioid antagonist: A substance that binds opioid receptors without activating them and blocks agonist effects. Antagonists oppose the receptor activation responsible for many opioid drug effects.
Gi/o protein: A family of heterotrimeric G proteins that inhibits adenylyl cyclase and regulates ion channels. Opioid receptor activation commonly signals through Gi/o proteins.
Kappa-opioid receptor: An opioid receptor subtype encoded by OPRK1 and activated by dynorphins and some drugs. It contributes to pain modulation and can produce dysphoria and other effects.
Naloxone: A medication that rapidly reverses many opioid effects by blocking opioid receptors. Its competitive antagonism can restore breathing during opioid overdose.
Opioid dependence: A physiological state in which stopping opioids can produce withdrawal symptoms. Neural adaptation to ongoing receptor stimulation can make abrupt cessation produce withdrawal.
Opioid agonist: A substance that binds and activates one or more opioid receptor types. Agonists directly stimulate receptors, unlike antagonists that prevent activation.

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