Related Experiment Video
Updated: Jun 28, 2026

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
Published on: July 29, 2014
Differential analgesic effects of a mu-opioid peptide, [Dmt(1)]DALDA, and morphine
Megumi Shimoyama1, Hazel H Szeto, Peter W Schiller
1Department of Anesthesiology, Teikyo University Chiba Medical Center, Ichihara, Chiba, Japan. shimoyama-teii@umin.ac.jp
Aims:
H-Dmt-D-Arg-Phe-Lys-NH(2) ([Dmt(1)]DALDA), a highly selective micro-opioid peptide, is potently analgesic after systemic and intrathecal administration but is less potent given intracerebroventricularly. This study was performed to further characterize the analgesic effects of [Dmt(1)]DALDA.
Methods:
We compared the effects of [Dmt(1)]DALDA and morphine after systemic administration in two different acute pain tests, the tail flick test and the paw withdrawal test, and examined how antagonizing the spinal opioid actions would affect their analgesic effects.
Results:
[Dmt(1)]DALDA was markedly more potent in the tail flick test than in the hot plate test, while the potencies of morphine were similar in the two tests. Intrathecal naloxone completely blocked the effect of systemic [Dmt(1)]DALDA in the tail flick test, while it only partially blocked the effect of morphine. At higher doses that produced analgesia in the hot plate test, the effect of [Dmt(1)]DALDA in this test was only partially blocked by naloxone.
Conclusion:
Systemic [Dmt(1)]DALDA has a unique analgesic property clearly different from that of morphine and it has a propensity to produce spinal analgesia.
Related Concept Videos
Opioid Analgesics: Synthetic and Semisynthetic Opioids
Analgesia and Pain Management
Opioid Receptors: Overview
Opioid Analgesics: Morphine and Other Natural Cogeners
Drugs Affecting GI Tract Motility: Opioids as Antidiarrheal Agents
Opioids, widely used antidiarrheal agents, mitigate diarrhea by slowing down...
Local Anesthetics: Differential Sensitivity of Nerve Fibers

