Opiate Receptors


Morphine and its congeners are considered to be the best painkilling agents available. The molecular basis for the observed analgesics effects and other pharmacological functions of opioid analgesic drugs are defined by multiple opioid receptors. The opioid receptors are typical G protein‐coupled receptors and activate a variety of downstream signalling pathways via G protein‐ or β‐arrestin‐dependent pathway. Because of the existence of multiple endogenous peptide ligands and the crosstalk with other nonreceptor signalling pathways or neurological circuitries, the pharmacological functions mediated by the multiple opioid receptors are quite complex and are involved in multiple physiological processes, such as the effects on the functions of immune cells and neural stem cells.

Key Concepts

  • The molecular basis for the observed pharmacological functions of opioid analgesic drugs is defined by multiple opioid receptors.
  • Signalling transduction from opioid receptors is essential for the functions of opioids.
  • As classical GPCR, agonist‐selective signalling can be observed with opioid receptors.
  • Opioid analgesic drugs and opioid receptors contribute to other CNS functions in addition to pain relief.
  • The observed pharmacological functions of opioid analgesic drugs involve nonreceptor elements.

Keywords: morphine; pain; G protein‐coupled receptor; endogenous peptides; central nerve system

Figure 1. Serpentine representation of the deduced amino acid sequence of the μ‐, δ‐ and κ‐opioid receptors. The blue circles represent the amino acids that are common to all three types of opioid receptors. The green circles represent the amino acids that are common to two of the opioid receptors. The open circles represent the amino acids that are different in all three opioid receptors. The leaders indicate the N‐terminus and C‐termini of the receptors.
Figure 2. Schematic representation of mouse μ‐opioid receptor gene.


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Further Reading

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Zheng, Hui, Law, Ping‐Yee, and Loh, Horace H(Feb 2020) Opiate Receptors. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0000290.pub2]