Opioid receptor

β-Endorphin, human is an agonist of opioid receptor, with preferred affinity for μ-opioid receptor and δ-opioid receptor. β-Endorphin exhibits anti-nociception activity by stimulating ε-opioid receptor, rather than μ-, δ-, and κ-opioid receptor. β-Endorphin has anti-nociception activity. Firstly, β-Endorphin combines together with the opioid receptors in hyperalgesia. Further, β-Endorphin suppresses the release of substance P at the level of spinal cord and blocks the conduction of pain on the primary sensory neurons. Moreover, β-Endorphin activates the endogenous analgesia system located in the CNS. In addition, β-Endorphin inhibits the conduction of pain and agitation of nociceptors to exert an analgesic effect.