| Receptor Subtype | μ (MOP, OP3) | δ (DOP, OP1) | κ (KOP, OP2) | NOP (ORL1, OP4) |
|---|
| G protein | Gi/o | Gi/o | Gi/o | Gi/o |
| Transduction Mechanism | Activation of inwardly rectifying K+ channels, inhibition of Ca2+ channels, inhibition of adenylyl cyclase |
| Localization in CNS | Anterior cingulate cortex, neocortex, amygdala, hippocampus, ventral dentate gyrus, presubiculum, nucleus accumbens, caudate putamen, thalamus, habenula, interpeduncular nucleus, pars compacta of the substantia nigra, superior and inferior colliculi, raphe nuclei | Medial habenula, hypothalamus, pons, medulla, dorsal root ganglion, caudate putamen, medial habenula, tegmentum, trigeminal nucleus | Claustrum, endopiriform nucleus, caudate putamen, nucleus accumbens, midline nuclear group of the thalamus, superficial grey layer of the superior colliculus, central grey, caudate putamen, nucleus accumbens, amygdala, thalamus, interpeduncular nuclei | Cortex, olfactory bulb, suprachiasmatic nucleus, amygdala, nucleus accumbens, thalamic nuclei, hypothalamus, hippocampus, septum, superior colliculus |
| Likely Physiological Roles | Respiration, cardiovascular functions, feeding, learning and memory, intestinal transit, locomotor activity, thermoregulation, hormone secretion, immune functions | Analgesia, motor integration, gastrointestinal motility, olfaction, respiration, cognitive function, mood driven behavior | Regulation of nociception, diuresis, feeding, neuroendocrine secretions | Motor and balance control, reinforcement and reward, nociception, the stress response, sexual behavior, aggression, autonomic control of physiological processes |
| Key Selective Agonists | Endomorphin-1 (1055)
Endomorphin-2 (1056)
DAMGO (1171)
| SNC 80 (0764)
SB 205607 (0921)
DPDPE (1431) | (±)-U-50488 (0495)
BRL 52537 (0699)
Dynorphin A (3195)
| Nociceptin (0910)
MCOPPB (3763) SCH 221510 (3240) |
| Key Selective Antagonists | β-Funaltrexamine (0926)
CTOP (1578)
Cyprodime (2601) | Naltrindole (0740)
Naltriben (0892)
BNTX maleate (0899) | nor-Binaltorphimine (0347)
DIPPA (0794)
GNTI (1282) | UFP-101 (1552)
(±)-J 113397 (2598)
JTC 801 (2481) |