Opioid GPCR Assays
Background of Opioid Receptors
Opiates are the most powerful analgesic molecules for clinical application and opioid receptors (OR) are part of the class A of G-protein coupled receptors targeting opiates. Activation of opioid receptors can inhibit the release of pain-related neurotransmitters and inhibit neurons by opening potassium channels that hyperpolarize and inhibit neurons.
Fig.1 Summary of opioid receptor signaling. (Al-Hasani, 2011)
Distribution and Functions of Opioid Receptors
Opioid receptors are mainly distributed in the brain, peripheral sensory neurons, spinal cord, as well as intestinal tract. The opioid receptors are mainly coupled to pertussis toxin-sensitive heterotrimeric Gαi/o proteins and inhibit adenylate cyclase (ACase). Activation of opioid receptors can modulate a variety of ion channels, including inhibition of voltage-dependent Ca2+ channels or activation of potassium channels.
Subtypes and Mechanisms of Opioid Receptors
To date, there are four types of receptor subtypes have been identified, including the δ opioid receptor, μ opioid receptor, κ opioid receptor, as well as orphan opioid receptor (NOP).
| Receptor | Gene | Mechanism | Agonists | Antagonists |
| δ Opioid receptor | OPRD1 |
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| μ Opioid receptor | OPRM1 |
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| κ Opioid receptor | OPRK1 |
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| NOP receptor | OPRL1 |
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Assay List of Opioid Receptors
Creative Biolabs can provide a range of assays of opioid receptors. You can choose the assay in the list or contact us for more information:
| Assay No. | Assay Name | Host Cell | Assay Type | Datasheet |
|---|---|---|---|---|
| cAMP Assay | ||||
| S01YF-1122-KX738 | Magic™ Rat OPRK1 In Vitro cAMP Assay | CHO-K1 | cAMP Assay | |
Published Data
| Paper Title |
The Role of Opioid Receptors in Immune System Function |
| Journal |
Frontiers in Immunology |
| Published | 2019 |
| Abstract |
Heroin and HIV infection spur research on opioids. These drugs are often immunosuppressive. The specificity of the receptor involved in immunosuppression was demonstrated to be the mu opioid receptor (MOR) by using pharmacological antagonists and MORgene-deficient mice. Morphine has been reported to have immunostimulatory effects through binding to myeloid differentiation factor-2 (MD-2), a molecule associated with the bacterial lipopolysaccharide (LPS) receptor toll-like receptor 4 (TLR4). This article demonstrates experimentally that morphine binds to TLR4, predictive of opioids being found to be pro-inflammatory. Furthermore, morphine is immunosuppressive in TLR4 receptor-deficient mice. |
| Result |
This article validates the immunosuppressive effect of morphine in animal and human cells expressing TLR4 and shows that the immunosuppressive effect can be blocked by antagonists of MOR or gene deletion of MOR. Thus, if morphine exerts its effects through TLR4 receptors, immune stimulation and the failure of MOR antagonists and MOR k/o mice to attenuate responses should be detected. However, the concept that opioids mediate their pharmacological effects through immune activation of TLR4 is not widely supported.
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Fig.2 Structures of alkaloid agonists and antagonists. (Eisenstein, 2019)
References
- Al-Hasani, R.; Bruchas, M. Molecular mechanisms of opioid receptor-dependent signaling and behavior. The Journal of the American Society of Anesthesiologists. 2011, 115(6): 1363-1381.
- Eisenstein, T.K. The role of opioid receptors in immune system function. Frontiers in Immunology. 2019, 10: 2904.
