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Updated: Jun 27, 2026

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
07:23

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities

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Strain-specific differences in modulatory effects of morphine on peritoneal inflammation in mice

Joanna Natorska1, Barbara Plytycz

  • 1Department of Evolutionary Immunobiology, Institute of Zoology, Jagiellonian University, R. Ingardena 6, 30-060 Kraków, Poland.

Folia Biologica
|December 9, 2008
PubMed

Insights

Morphine co-injection with zymosan reduced pain and leukocyte accumulation in most mouse strains, but effects varied by strain. Naltrexone reversed these morphine impacts, indicating opioid receptor involvement.

Area of Science:

  • Pharmacology
  • Immunology
  • Neuroscience

Background:

  • Local administration of high-dose morphine with a proinflammatory agent can exhibit anti-inflammatory effects.
  • These effects are not consistent across all mouse strains.
  • Zymosan-induced peritonitis is a model to study inflammation and pain responses.

Purpose of the Study:

  • To compare the behavioral and cellular consequences of morphine co-injection during zymosan-induced peritonitis across different mouse strains.
  • To investigate the dose- and strain-specific effects of morphine on pain, locomotion, and leukocyte accumulation.
  • To determine the role of opioid receptors in morphine's effects using naltrexone.

Main Methods:

  • Male mice from C57C3H, Swiss, Balb/c, C57BL/6, and CBA strains were injected with zymosan and/or morphine.
  • Different doses of morphine (0-20 mg/kg) were administered, with or without naltrexone pretreatment.
  • Behavioral assessments (pain, locomotion) and cellular analysis (leukocyte accumulation) were performed.

Main Results:

  • Morphine abolished pain symptoms in all strains and affected locomotion in a dose- and strain-specific manner.
  • High-dose morphine inhibited leukocyte and polymorphonuclear cell accumulation in all strains except CBA.
  • Naltrexone reversed the anti-inflammatory and anti-nociceptive effects of morphine, and morphine inhibited leukocyte chemotaxis in vitro.

Conclusions:

  • Morphine exerts strain-specific effects on peritonitis, impacting pain, locomotion, and inflammation.
  • Opioid receptors mediate the anti-inflammatory and anti-nociceptive actions of morphine in this model.
  • Mouse strain differences are critical for understanding morphine's complex effects on inflammation and pain.

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