Effect of opioid receptor ligands on the μ-S196A knock-in and μ knockout mouse vas deferens

Philip S. Portoghese, Ping Yee Law, Horace H. Loh

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3 Scopus citations


We have determined the effect of naltrexone, naloxone, [D-Ala 2,D-Leu5]enkephalin (DADLE), and morphine on the μ-S196A opioid receptor knock-in and μ-opioid receptor knockout mouse vas deferens preparations. The antagonists, naltrexone and naloxone, exhibited agonist activity and possessed IC50 values that were 14- and 37-fold greater than morphine on the S196A preparation. Morphine was found to be threefold more potent at S196A relative to wild-type μ-opioid receptor. The mouse vas deferens data suggest that S196 in transmembrane helix 4 of the μ-opioid receptor modulates efficacy. It is proposed that this may be due to decreased dimerization of the receptor. Identical IC50 values of DADLE obtained on the wild-type, S196A knock-in, and μ-opioid receptor knockout preparations support the absence of μ-δ heterodimers in the mouse vas deferens.

Original languageEnglish (US)
Pages (from-to)207-210
Number of pages4
JournalEuropean Journal of Pharmacology
Issue number2-3
StatePublished - Oct 8 2003

Bibliographical note

Funding Information:
We thank Mary Lunzer for conducting the mouse vas deferens experiments. This research was supported by NIH research grants DA01533 (PSP), DA07339, DA0564, DA11806, KO5-DA70554 (HHL) and KO5-DA-00513 (PYL).


  • Mouse
  • Opioid receptor antagonist
  • Vas deferens
  • μ-Opioid receptor knockout
  • μ-Ser196Ala


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