mu-Opposing actions of the kappa-opioid receptor

Trends Pharmacol Sci. 1998 Mar;19(3):94-8. doi: 10.1016/s0165-6147(98)01169-9.


Pharmacological studies and recent research using genetic approaches have indicated that most actions of exogenous opioids, such as morphine, are mediated through the mu-opioid receptor. By contrast, the function of the kappa-opioid receptor in opioid actions largely remains unclear. In this article, Zhizhong Z. Pan discusses the accumulating evidence that activation of the kappa-receptor antagonizes various mu-receptor-mediated actions in the brain, including analgesia, tolerance, reward and memory processes. The neural mechanism for this potentially ubiquitous mu-opposing function of the kappa-receptor is believed to involve distinct locations of the two opioid receptors on physiologically different cell types in local neuronal networks that are implicated in an opioid action.

Publication types

  • Review

MeSH terms

  • Analgesics, Opioid / pharmacology*
  • Animals
  • Humans
  • Receptors, Opioid, kappa / drug effects
  • Receptors, Opioid, kappa / physiology*
  • Receptors, Opioid, mu / drug effects
  • Receptors, Opioid, mu / physiology*


  • Analgesics, Opioid
  • Receptors, Opioid, kappa
  • Receptors, Opioid, mu