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Updated: Aug 23, 2026

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
Published on: July 29, 2014
Opioid receptor binding and in vivo antinociceptive activity of position 3-substituted morphiceptin analogs
Jakub Fichna1, Jean-Claude do-Rego, Jean Costentin
1Department of Medicinal Chemistry, Medical University, Lodz, Poland.
Abstract:
Analogs of morphiceptin (Tyr-Pro-Phe-Pro-NH2), a mu-selective opioid receptor ligand, with position 3-modifications, including altered size, lipophilicity, and electronic character, while maintaining aromaticity were synthesized. The activity of the new analogs in in vitro assays and in in vivo hot-plate test of analgesia was compared and the results were consistent. [D-1-Nal3]Morphiceptin was the most potent analog of this series with a 26-fold increase in mu-opioid receptor affinity, a 15-fold potency increase in the GPI assay, and a significant potency increase in the hot-plate analgesic test, as compared with morphiceptin. [d-Qal3]Morphiceptin was found to be a weak antagonist in the GPI assay.
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