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A new and sensitive method for measuring thermal nociception in cutaneous hyperalgesia
K Hargreaves1, R Dubner, F Brown
1Neurobiology and Anesthesiology Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892 U.S.A.
Pain
|January 1, 1988
Summary
A new automated method accurately measures thermal hyperalgesia in animals without causing distress. This thermal stimulation technique offers greater sensitivity than traditional mechanical methods for assessing pain responses.
Area of Science:
- Neuroscience
- Pharmacology
- Animal Models
Background:
- Cutaneous hyperalgesia is a key indicator of pain and inflammation.
- Assessing thermal hyperalgesia in unrestrained animals presents methodological challenges.
- Existing methods may lack sensitivity or introduce confounding factors like repeated testing stress.
Purpose of the Study:
- To describe a novel, automated method for measuring cutaneous hyperalgesia to thermal stimulation in unrestrained animals.
- To evaluate the sensitivity and utility of this thermal method compared to a mechanical method (Randall-Selitto).
- To assess the impact of carrageenan-induced inflammation on thermal nociceptive thresholds.
Main Methods:
- An automated behavioral detection system was employed to measure paw withdrawal latency in response to thermal stimuli.
- Carrageenan was used to induce inflammation in animal paws, with saline as a control.
- The novel thermal method and the Randall-Selitto mechanical method were used to assess hyperalgesia and its blockade by morphine and indomethacin.
Main Results:
- The automated thermal method successfully measured hyperalgesia in inflamed paws, indicated by significantly shorter withdrawal latencies.
- Carrageenan-induced inflammation led to a decreased thermal nociceptive threshold.
- Both thermal and mechanical methods detected dose-related hyperalgesia and its blockade by analgesics, but the thermal method demonstrated superior bioassay sensitivity.
Conclusions:
- The described automated thermal stimulation method provides a sensitive and reliable way to measure cutaneous hyperalgesia in unrestrained animals.
- This method avoids the confounding effects of repeated testing on hyperalgesia development.
- The thermal method offers advantages over mechanical methods, including enhanced sensitivity and the ability to measure additional behavioral parameters.