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Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
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Nociceptive behavior following hindpaw burn injury in young rats: response to systemic morphine

Shuxing Wang1, Lin Zhang, Yuxin Ma

  • 1MGH Center for Translational Pain Research, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.

Pain Medicine (Malden, Mass.)
|December 15, 2010
PubMed

Insights

A new burn injury model in young rats effectively mimics pain responses and molecular changes seen in pediatric burn patients. This model helps study pain mechanisms and differences between young and adult rats.

Area of Science:

  • Pain research
  • Animal models of injury
  • Pediatric pain management

Background:

  • Pediatric burn injury pain management remains a significant clinical challenge.
  • Understanding age-specific pain mechanisms is crucial for effective treatment.

Purpose of the Study:

  • To establish a reliable burn injury model in young rats (3-4 weeks old).
  • To investigate pain behaviors and molecular changes following burn injury in young rats.
  • To compare pain development and morphine response in young versus adult burn-injured rats.

Main Methods:

  • A burn injury was induced using a hot water bath (85°C, 12 seconds) on the hindpaw of young rats under anesthesia.
  • Nociceptive behaviors, including mechanical allodynia and thermal hyperalgesia, were assessed.
  • Spinal cord dorsal horn tissue was analyzed for changes in receptor and enzyme expression.
  • The efficacy of dextromethorphan, an N-methyl-D-aspartate (NMDA) receptor antagonist, was evaluated.

Main Results:

  • Burn injury induced significant mechanical allodynia and thermal hyperalgesia in young rats.
  • Upregulation of NMDA receptor subunit NR1, Akt1, Akt2, and PKCγ was observed in the spinal cord.
  • Downregulation of neuronal nitric oxide synthase (NOS) and glycogen synthase kinase-3β occurred.
  • Dextromethorphan treatment attenuated burn injury-induced pain behaviors.
  • Young rats did not exhibit spontaneous tolerance to morphine's analgesic effects, unlike adult rats.

Conclusions:

  • This young rat burn injury model is suitable for studying nociception mechanisms.
  • The model allows for differentiation of burn injury sequelae between young and adult rats.
  • Findings suggest age-dependent differences in pain development and opioid tolerance post-burn injury.
Abstract

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