The mu-opioid receptor is necessary for [D-Pen2,D-Pen5]enkephalin-induced analgesia

Eur J Pharmacol. 1997 Apr 18;324(2-3):R1-2. doi: 10.1016/s0014-2999(97)10016-4.


Interactions between delta-opioid receptors and morphine-preferring mu-opioid receptor subtypes have been suggested. Availability of transgenic mu-opioid receptor knockout mice allows assessment of mu-opioid receptor roles in the analgesia produced by the classical delta-opioid receptor agonist [D-Pen2,D-Pen5]enkephalin (DPDPE) in hot-plate and tail-flick tests. DPDPE analgesia was dramatically reduced in mu-opioid receptor knockout mice in a gene-dose-dependent fashion. The analgesia induced by this classic delta-opioid receptor agonist depends on intact mu-opioid receptors, suggesting that selective delta-opioid receptor drugs may require mu-opioid receptor occupancies for full efficacy.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Analgesia*
  • Analgesics*
  • Animals
  • Enkephalin, D-Penicillamine (2,5)-
  • Enkephalins*
  • Mice
  • Mice, Knockout
  • Mice, Transgenic
  • Receptors, Opioid, mu / agonists
  • Receptors, Opioid, mu / genetics
  • Receptors, Opioid, mu / metabolism*


  • Analgesics
  • Enkephalins
  • Receptors, Opioid, mu
  • Enkephalin, D-Penicillamine (2,5)-