Articles: hyperalgesia.
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Experimental neurology · Aug 2006
Comparative StudyPivotal involvement of neurogenic mechanism in subcutaneous bee venom-induced inflammation and allodynia in unanesthetized conscious rats.
The bee venom (BV) model is a valid inflammatory pain model in animals and has been extended to human studies using its principle protein, mellitin. After subcutaneous (s.c.) injection of BV, long-lasting spontaneous nociception followed by thermal hyperalgesia, static allodynia, and local inflammatory response (edema) can be observed in rats. We hypothesize that (1) neurogenic components may contribute to the BV-induced inflammatory response and (2) static and dynamic mechanical allodynia may exist simultaneously in the BV model. ⋯ Local capsaicin onto the sciatic nerve produced a significant inhibition of the BV-induced decrease in the paw withdrawal mechanical threshold, but not the paw withdrawal latency, of the injected paw. These findings suggest that neurogenic components, via dorsal root reflex and axon reflex mechanisms, are probably involved in the maintenance and the development of the BV-induced inflammation. In addition, the capsaicin-sensitive primary afferents may play differential roles in the development of the BV-induced static and dynamic mechanical allodynia.
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J. Neurosci. Methods · Jul 2006
Characterization of hind paw licking and lifting to noxious radiant heat in the rat with and without chronic inflammation.
The paw withdrawal latency to thermal radiant heat stimuli is a widely used nociceptive measure to study hyperalgesic mechanisms. In the present study, in addition to the paw withdrawal latency, two behavioral components of pain behaviors, paw licking and paw lifting have been characterized and quantified. The thermal stimuli were successively applied to the plantar surface of the rat hind paws and recorded the behavioral responses to each of the stimuli. ⋯ The paw withdrawal latency decreased in inflamed rats in comparison with control rats. These data informs that noxious radiant heat specifically evokes the frequency of paw lifting behavior in normal physiological condition, and paw licking behavior in a pathological inflammatory condition. These findings suggest that in addition to the measurement of PWL, scoring of paw licking and lifting behaviors will improve the sensitivity of this pain test.
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Hyperbaric oxygen therapy has been used to treat a variety of ailments from carbon monoxide poisoning to fibromyalgia. The purpose of this experiment was to explore the effect of hyperbaric oxygen treatment on carrageenan-induced inflammation and pain in rats. Hyperbaric oxygen treatment significantly decreased inflammation and pain following carrageenan injection. Clinically hyperbaric oxygen may be used in situations where NSAIDS are contraindicated or in persistent cases of inflammation.
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Comparative Study
Quantitative sensory testing in children with migraine: preliminary evidence for enhanced sensitivity to painful stimuli especially in girls.
Recent studies showed an enhanced general sensitivity to painful stimuli in adult migraineurs during as well as between attacks. Yet, the influence of a prolonged pain history and potential sex differences has not been studied. We used quantitative sensory testing to examine 25 children with migraine between attacks and 28 controls (age 9-15). ⋯ To summarize, an enhanced sensitivity to painful stimuli can already be observed in children suffering from migraine for an average duration of 4.4 years. This may be the result of sensitization in nociceptive pain pathways caused by frequent pain experiences. Girls with migraine were more prone to such sensitization, which may increase their risk for continuing to suffer from migraine throughout adulthood.
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Intradermal capsaicin is a human pain model that produces reliable pain and sensitization. This model facilitates controlled testing of analgesic efficacy via a crossover design while minimizing confounding variables in clinical pain states and retaining sufficient power with small samples. ⋯ The 10 and 100 microg capsaicin doses produced robust pain measures across a range of modalities, and lower doses produced minimal effects. Whereas most studies use 100 microg, using a lower dose is reasonable and may facilitate detection of subtle analgesic effects--particularly with nonopioid analgesics--and drugs can be tested in lower doses, minimizing adverse side effects.