Spinal analgesic actions of the new endogenous opioid peptides endornorphin-1 and -2

Laura S. Stone, Carolyn A. Fairbanks, Tinna M. Laughlin, H. Oanh Nguyen, Tina M. Bushy, Martin W. Wessendorf, George L. Wilcox

Research output: Contribution to journalArticlepeer-review

200 Scopus citations


Two highly-selective μ-opioid receptor agonists, endomorphin-1 and -2, were recently purified from bovine brain and are postulated to be endogenous μ-opioid receptor ligands. We sought to determine the effects of these ligands at the spinal level in mice. Endomorphin-1 and -2 produced short acting, naloxone-sensitive antinociception in the tail flick test and inhibited the behavior elicited by intrathecally injected substance P. Both endomorphin-1 and -2 were anti-allodynic in the dynorphin-induced allodynia model. Although acute tolerance against both endomorphins developed rapidly, endomorphin-1 required a longer pretreatment time before tolerance was observed. We conclude that the endomorphins are potent spinal antinociceptive and anti-allodynic agents and that they or related compounds may prove therapeutically useful as spinal analgesics.

Original languageEnglish (US)
Pages (from-to)3131-3135
Number of pages5
Issue number14
StatePublished - 1997


  • Allodynia
  • Autinociception
  • Dynorphin
  • Endomorphin
  • Intrathecal
  • Mice
  • Opioid
  • Subst ance P
  • Tall flick
  • Tolerance


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