Opioid GPCR Family Subtypes and Products

What Are Opioid Receptors?

Opioid receptors are a family of G protein-coupled receptors (GPCRs) comprised of five receptor subtypes: delta, kappa, mu, nociceptin receptor, and zeta. Opioid receptors are found all throughout the brain, spinal cord, and digestive tract. They play a major role in a variety of functions including analgesia, anti-depression, anxiety, euphoria, appetite, and sedation. There are currently a large host of clinical drugs that target the mu receptor for its analgesic effects, such as morphine and naloxone.

Opioid Receptor Information

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δ opioid receptor (DOR) inhibits neurotransmitter release by reducing Ca++ currents and increasing K+ conductance. In rats, morphine tolerance is associated with DOR-mediated activation of cortical CCKergic systems. There are indications that some DOR antagonists produce potent antitussive effects and may be considered as candidates of antitussive drugs. In contrast, some DOR agonists have shown antinociceptive, seizuregenic and convulsive properties, implicating a role for the DOR in depression. Early clinical experiments have demonstrated that exogenously administered opioid peptides had antidepressant activity in human patients, suggesting that the receptor may provide a new therapeutic target for treating depression.

κ Opioid Receptor (KOR) is a receptor for dynorphins. KOR inhibits neurotransmitter release by reducing calcium currents and increasing potassium conductance and may play a role in arousal and regulation of autonomic and neuroendocrine functions. Some studies suggest that stimulation of KOR improves memory dysfunctions resulting from the blockade of muscarinic M1 receptors. In addition, KOR agonists attenuate several behavioral responses induced by drugs of abuse, raising the possibility that KOR agonists may be useful for the treatment of dependence on drugs of abuse.

μ opioid receptor (MOR) is a G protein-coupled receptor for β-endorphin. The receptor activation inhibits neurotransmitter release by reducing calcium currents and increasing potassium conductance. MOR mediates positive reinforcement following direct (morphine) or indirect (alcohol, cannabinoids, nicotine) activation. MOR plays a genetic role in the control of gut inflammation. MOR-deficient mice are highly susceptible to colon inflammation, with a 50% mortality rate occurring 3 days after administration of TNBS that induces inflammation. MOR agonists regulate cytokine production and T cell proliferation and might be new therapeutic molecules in inflammatory bowel disease.

NOP, ORL1 or OPRL1 (opioid receptor-like 1 receptor) is also known as nociceptin receptor, orphanin FQ receptor and KOR-3 (kappa 3-related opioid receptor). It is a receptor for the neuropeptide nociceptin/orphanin FQ and has a potential role in modulating a number of brain functions, including instinctive behaviors and emotions. In vivo experiments have demonstrated that nociceptin modulates a variety of biological functions including nociception, food intake, memory processes, cardiovascular and renal functions, spontaneous locomotor activity, gastrointestinal motility, anxiety and neurotransmitter release at peripheral and central sites.

Opioid Cell Lines

Receptor FamilyReceptorSpeciesParentalStable Cell Lines Division-Arrested Cells Membranes
deltahumanCHO-K1 Gαqi5CG1351-1DCG1351-1MCG1351-1
deltaratCHO dhfr-C1351DC1351MC1351
kappahumanCHO-K1 Gαqi5CG1352-1DCG1352-1MCG1352-1
kappahumanCHO-K1 β-Arrestin2CA1352BA2-1DCA1352BA2-1MCA1352BA2-1
kapparatCHO dhfr-C1352-1DC1352-1MC1352-1
kapparatCHO dhfr-Cr1352-8DCr1352-8MCr1352-8
muhumanCHO-K1 Gαqi5CG1350-1aDCG1350-1aMCG1350-1a
muratCHO dhfr-Cr1350-1aDCr1350-1aMCr1350-1a
mu Mutant Y150FhumanCHO-K1C1350-1MT1DC1350-1MT1MC1350-1MT1
mu Mutant Y150AhumanCHO-K1C1350-1MT2DC1350-1MT2MC1350-1MT2
mu Mutant M153AhumanCHO-K1C1350-1MT3DC1350-1MT3MC1350-1MT3
mu Mutant H299NhumanCHO-K1C1350-1MT4DC1350-1MT4MC1350-1MT4
mu Mutant H299AhumanCHO-K1C1350-1MT5DC1350-1MT5MC1350-1MT5
NOPhumanCHO-K1 Gαqi5CG1354-1DCG1354-1MCG1354-1
NOPhumanCHO-K1 β-Arrestin2CA1354-1DCA1354-1MCA1354-1
NOPratCHO dhfr-Cr1354DCr1354MCr1354