Opioid Receptors are G protein-coupled receptors (GPCRs). They mediate the response of most hormones, neurotransmitters, and drugs. Therefore, they play important role in sensory perception of vision, taste, and olfaction. There are three classical opioid receptors (μ, δ, and κ receptor), while the novel nociceptin receptor (NOR) is a non-opioid branch of the opioid receptor family. Opioids can act at these receptors as agonists, antagonists, or partial agonists. The classical opioid receptors widely exist in the central nervous system and, to a lesser extent, throughout the periphery, occupying sites within the vas deferens, knee joint, gastrointestinal tract, heart, and immune system, amongst others.
Quantitatively, the μ-opioid receptor (MOR) is the most abundant of all the opioid receptors. Besides, MOR widely exist in dense labeling throughout the fore, mid and hindbrain regions in the CNS. The MOR subtype is the therapeutic target for most currently used opioids. The agonism of MOR has become an analgesic or antidepressant strategy. For example, Morphine is a well-known μ-opioid receptor (MOR) agonist and an efficient analgesic. Here, we will introduce another μ-opioid receptor agonist, NAQ.
NAQ is a potent and selective μ-opioid receptor partial agonist.
NAQ shows selectivity for Mu opioid receptor over the δ receptor and the κ receptor. What’s more, A single treatment of NAQ antagonizes the antinociceptive effects of Morphine in the mouse tail immersion test. Moreover, NAQ produces weak intracranial self-stimulation (ICSS) facilitation in rats but more robust ICSS facilitation during and after Morphine treatment and also reverses Morphine withdrawal-associated depression of ICSS. Therefore, NAQ has the potential for research on opioid withdrawal or dependence.
All in all, NAQ is a potent and selective μ opioid receptor partial agonist. NAQ has the potential for research on opioid withdrawal or dependence.