Mu opioid receptor, Delta opioid receptor, Kappa opioid receptor (MOR, DOR, KOR)

The mu, delta, and kappa opioid receptors are three closely related but molecularly distinct G protein-coupled receptors that mediate the physiological and pharmacological effects of endogenous and exogenous opioid compounds. MORs are primarily responsible for analgesic and euphoric effects as well as adverse outcomes such as respiratory depression and addiction. DORs have roles in analgesia, mood regulation, and neuroprotection, and are emerging as targets for psychiatric and neurological disorders. KORs also mediate analgesia but are associated with dysphoria and antireward effects; they are being actively explored for pain, addiction, and mood disorders. All three are widely expressed in the central and peripheral nervous systems and function by inhibiting neuronal excitability and neurotransmitter release, primarily via Gi/o signaling pathways. Their structural dynamics and biased signaling properties are key areas of current research, informing the development of safer and more selective therapeutic agents[1][3][5][6].

Other names

μ-opioid receptor (mu opioid receptor)δ-opioid receptor (delta opioid receptor)κ-opioid receptor (kappa opioid receptor)MOR, DOR, KOROpioid receptor familyOpioid peptide receptorOPRM1 (mu, gene)OPRD1 (delta, gene)OPRK1 (kappa, gene)

Agonism at GPCRs leading to Gi/o protein signaling (inhibition of adenylyl cyclase, decreased cAMP, reduced neurotransmitter release) Induction of potassium channel opening (hyperpolarization) Inhibition of calcium channel activity (reduced neurotransmitter release) Biased agonism (favoring G-protein vs. β-arrestin signaling) Antagonism (competitive blockade of receptor)[3][5][6]