Articles: hyperalgesia.
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Spinal glutamate transporters (GT) have been implicated in the mechanisms of neuropathic pain; however, how spinal GT uptake activity is regulated remains unclear. Here we show that alteration of spinal arachidonic acid (AA) turnover after peripheral nerve injury regulated regional GT uptake activity and glutamate homeostasis. Chronic constriction nerve injury (CCI) in rats significantly reduced spinal GT uptake activity ((3)H-glutamate uptake) with an associated increase in extracellular AA and glutamate concentration from spinal microdialysates on postoperative day 8. ⋯ Consistent with these findings, AACOCF3 reduced the development of both thermal hyperalgesia and mechanical allodynia, whereas diclofenac exacerbated thermal hyperalgesia, in CCI rats. Thus, spinal AA turnover may serve as a regulator in CCI-induced changes in regional GT uptake activity, glutamate homeostasis, and neuropathic pain behaviors. These data suggest that regulating spinal AA turnover may be a useful approach to improving the clinical management of neuropathic pain.
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Opioid tolerance and opioid-induced hyperalgesia are conditions that negatively affect pain management. Tolerance is defined as a state of adaptation in which exposure to a drug induces changes that result in a decrease of the drug's effects over time. Opioid-induced hyperalgesia occurs when prolonged administration of opioids results in a paradoxic increase in atypical pain that appears to be unrelated to the original nociceptive stimulus. ⋯ Pain facilitatory mechanisms in the central nervous system are known to contribute to opioid-induced hyperalgesia. Recent research indicates that there may be overlap in the two conditions. This article reviews known and hypothesized pathophysiologic mechanisms surrounding these phenomena and the clinical implications for pain management nurses.
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Randomized Controlled Trial Clinical Trial
Brain imaging of analgesic and antihyperalgesic effects of cyclooxygenase inhibition in an experimental human pain model: a functional MRI study.
One of the most distressing symptoms of many neuropathic pain syndromes is the enhanced pain sensation to tactile or thermal stimulation (hyperalgesia). In the present study we used functional magnetic resonance imaging (fMRI) and explored brain activation patterns during acute impact pain and mechanical hyperalgesia in the human ultraviolet (UV)-B model. To investigate pharmacological modulation, we examined potential differential fMRI correlates of analgesic and antihyperalgesic effects of two intravenous cyclooxygenase inhibitors, i.e. parecoxib and acetylsalicylic acid (ASA). ⋯ These brain areas were also modulated under antihyperalgesic conditions. However, we observed a greater drug-induced modulation of mainly PA and inferior frontal cortex during mechanical hyperalgesia; during acute mechanical pain there was a greater modulation of mainly bilateral S2. Therefore, the results of the present study suggest that there is a difference in the brain areas modulated by analgesia and antihyperalgesia.
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Complex regional pain syndromes (CRPS) have been recognized with increasing frequency in children. These disorders appear to differ markedly from those observed in adults. The International Association for the Study of Pain diagnostic criteria for CRPS were developed based on adult studies; these criteria have not been validated for children. ⋯ There was a significant correlation between mechanical dynamic allodynia and allodynia to punctate temporal summation (P<0.001). As with adult CRPS, the thermal and mechanical sensory abnormalities appear in different combinations in different patients with similar clinical presentations. In a majority of patients, the pathogenesis of pain is seemingly of central origin.
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Neurogastroenterol. Motil. · Sep 2007
Long-term colonic hypersensitivity in adult rats induced by neonatal unpredictable vs predictable shock.
Our goal was to examine the relationship between early life trauma and the development of visceral hypersensitivity in later life in irritable bowel syndrome (IBS). Rat pups underwent neonatal conditioning: (i) paired odour-shock, where odour is a predictable shock signal, (ii) unpaired odour-shock, where odour is an unpredictable shock signal or (iii) control odour-only with odour presentations and handling without shock. At maturity, colorectal sensitivity was measured as a visceromotor behavioural response. ⋯ Adult responses to CRD were altered by infant experience with shock trauma. However, depending on the context of that early life trauma, there are major differences between the long-term effects of that early life trauma on colonic sensitivity compared to controls. These results strengthen the link between early life trauma and adult IBS, and suggest that unpredictable trauma is a critical factor for later life disorders.