Mu-opioid receptor and Delta-opioid receptor (MOR, DOR; for heteromer: MOR-DOR heteromer, mu-delta opioid receptor complex (no canonical))

Mu-opioid receptor and delta-opioid receptor are two major members of the opioid receptor family, which belong to the G protein-coupled receptor (GPCR) superfamily and play critical roles in the modulation of pain, mood, and many other neurophysiological processes[5][6][9]. They are activated by endogenous opioid peptides (endorphins for MOR, enkephalins for DOR) and by many therapeutic or abused drugs (e.g., morphine acts primarily on MOR, but also has some activity at DOR)[5][9]. Recent research suggests these receptors can form homo- and heteromers (e.g., MOR-DOR heteromers), potentially leading to novel signaling behaviors and pharmacological profiles, but these complexes are not yet considered fully canonical therapeutic targets[2]. Opioid receptors are distributed throughout the central and peripheral nervous system, with distinct but overlapping physiological and pathological roles[5][6][9]. Note: If you need a singular, canonical structured record, separate entries for "Mu-opioid receptor" and "Delta-opioid receptor" should be used. If studying or referencing a hypothesized mu–delta heteromer/complex, clearly specify this as "mu–delta opioid receptor heteromer" and document as non-canonical/experimental for most major databases.

Other names

mu receptorμ receptorMOROPRM1delta receptorδ receptorDOROPRD1mu–delta opioid receptor heteromerMOR-DOR heteromermu/delta opioid receptor complex

Agonists: Activate inhibitory G protein pathways, reduce cyclic AMP, inhibit neurotransmitter release, induce membrane hyperpolarization via potassium currents, reduce neuronal excitability. Antagonists: Block endogenous and exogenous ligand binding, reverse opioid effects. Partial agonism, biased agonism, inverse agonism (dependent on drug and receptor subtype/complex).