Articles: hyperalgesia.
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Comparative Study
Reliability of pain threshold measurement in young adults.
The objective was to examine reliability of pressure and thermal (cold) pain threshold assessment in persons less than 25 years of age, using intra-class correlation (ICC) and coefficients of repeatability and variability. We measured thresholds to pain from pressure algometry and ice placed at the hand and head in 10 healthy volunteers aged 18-25. Intra-rater reliability was examined with ICC. ⋯ Reliability of repeat assessments was high as assessed by ICC, although coefficients of repeatability and variation indicated considerable inter-individual variation in repeat measurements. Pressure algometry and strategically placed ice appear to be reliable techniques for assessing pain processing in young adults. Reliability studies employing ICC may benefit from complementary estimation of CR and CV.
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Wien. Klin. Wochenschr. · Feb 2006
Controlled Clinical TrialHyperalgesia against capsaicin in persons with un-investigated dyspepsia: potential as a new diagnostic test.
Lack of understanding of the pathogenesis of functional dyspepsia is one reason for the paucity of effective treatment options. Whereas mechanical sensitivity in persons suffering from dyspepsia might be impaired, chemically induced hypersensitivity has received little attention. The aim of this study was to evaluate whether vanilloid receptors stimulated by capsaicin are hypersensitive in persons with dyspepsia. ⋯ Jejunal sensitivity to capsaicin is increased in persons with un-investigated dyspepsia, and vanilloid receptors might be involved in the pathophysiology of this condition. Patients with hypersensitivity to chemical stimuli may represent a distinct subpopulation based on the underlying pathophysiology and may require specific treatment to restore normal visceral sensitivity.
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Comparative Study
Erythropoietin reduces Schwann cell TNF-alpha, Wallerian degeneration and pain-related behaviors after peripheral nerve injury.
Chronic sciatic nerve constriction injury (CCI) induces Wallerian degeneration and exaggerated pain-like behaviors. These effects are mediated in large part by pro-inflammatory cytokines, such as tumor necrosis factor alpha (TNF-alpha). In this study, we demonstrate that systemically administered recombinant human erythropoietin (rhEpo) facilitates recovery from chronic neuropathic pain associated with CCI in rats. ⋯ RhEpo inhibited TNF-alpha expression in response to lipopolysaccharide, supporting the conclusions of our in vivo CCI experiments. In addition, rhEpo directly counteracted Schwann cell death induced by exogenously added TNF-alphain vitro. These results indicated that rhEpo regulates TNF-alpha by multiple mechanisms; rhEpo regulates TNF-alpha mRNA expression by Schwann cells but also may directly counteract TNF-alpha signaling pathways that lead to injury, chronic pain and/or death.
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Chemical and cold sensitivity of two distinct populations of TRPM8-expressing somatosensory neurons.
The cold- and menthol-sensing TRPM8 receptor has been proposed to have both nonnociceptive and nociceptive functions. However, one puzzle is how this single type of receptor may be used by somatosensory neurons to code for two distinct sensory modalities. Using acutely dissociated rat dorsal root ganglion (DRG) neurons without culture, we show that TRPM8 receptors are expressed on two distinct classes of somatosensory neurons. ⋯ Furthermore, low concentrations of menthol produce strong selection of the MS/CIS neuron population over the MS/CS neuron population. On the other hand, the population selection becomes weaker with higher concentrations of menthol. TRPM8 current density shows significant higher in MS/CIS neurons than in MS/CS neurons, suggesting different expression levels of TRPM8 receptors between the two neuron populations, and this difference may provide a mean of selective activation of MS/CIS neurons at low stimulation intensity.
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J. Pharmacol. Exp. Ther. · Feb 2006
High-efficacy 5-hydroxytryptamine 1A receptor activation counteracts opioid hyperallodynia and affective conditioning.
Pain may become intractable as tolerance develops to opioids and the opioids, paradoxically, induce pain. We examined the hypothesis that the analgesia produced by the novel analgesic and high-efficacy 5-hydroxytryptamine (5-HT)(1A) receptor agonist (3-chloro-4-fluoro-phenyl)-[4-fluoro-4-[[(5-methyl-pyridin-2-ylmethyl)-amino]methyl]piperidin-1-yl]methanone, fumaric acid salt (F 13640) may counteract opioid-induced pain. In studies of the somatosensory quality of pain in infraorbital nerve-injured rats, morphine infusion (5 mg/day) by means of osmotic pumps initially caused analgesia (i.e., decreased the behavioral response to von Frey filament stimulation), followed by hyperallodynia and analgesic tolerance. ⋯ The data confirm that opioids produce bidirectional hypo- and proalgesic actions, and offer initial evidence that high-efficacy 5-HT(1A) receptor activation counteracts both the sensory and the affective/motivational qualities of opioid-induced pain. The data also indicate that F 13640 may be effective with opioid-resistant pain. It further is suggested that opioid addiction may represent self-therapy of opioid-induced pathological pain.