Articles: neuropathic-pain.
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Orthop Traumatol Sur · Nov 2014
Observational StudyChronic pain 1 year after foot surgery: Epidemiology and associated factors.
Most studies of chronic postoperative pain focussed on major surgical procedures. Chronic postoperative pain occurred in 10% to 50% of patients and exhibited neuropathic features in 5% to 68% of cases. The objectives of this prospective single-centre study were to determine the rates of occurrence and associated factors of any chronic pain and of neuropathic chronic pain 1 year after orthopaedic surgery on the foot. ⋯ IV, prospective observational longitudinal cohort study.
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The aim of this study was to investigate the predictive value of exercise-induced hypoalgesia (EIH) profile on pain intensity induced by nerve injury in a rat model. EIH was tested by evaluating the percentage of withdrawal responses to a train of 30 mechanical stimuli on the hind paw before and after 180 seconds of exercise on a rotating rod. The rats were grouped into low, medium, and high EIH based on their reduction in the percentage of withdrawal responses before and after exercise. Rats from each group then underwent left sciatic nerve constriction injury. Mechanical allodynia, mechanical hyperalgesia, and heat allodynia were assessed in the affected and contralateral hind paws prior to and 3 and 7 days following the procedure. The low EIH rats demonstrated increased hypersensitivity at baseline and developed significantly more severe heat allodynia, mechanical allodynia, and hyperalgesia 3 and 7 days following the injury compared to the medium and high EIH rats. Moreover, the low EIH rats developed contralateral heat allodynia following the injury. The EIH of habituated and nonhabituated rats was compared to study the role of stress on the hypoalgesic effect. No significant differences were found between the habituated and nonhabituated rats at baseline and 1 and 5 minutes after the exercise. ⋯ EIH profile was found to be predictive of pain severity following nerve injury. It may suggest that selected patients with faulty pain modulation are at risk for developing chronic pain following injury or surgical procedures. EIH may represent a preoperative means to detect this predisposition and enable proactive management.
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Inflammation plays a key role in the development of sensitization after peripheral nerve damage. We recently demonstrated that tumor necrosis factor-α receptor (TNFR) levels in the spinal cord correlate with pain sensation in herniated disc patients in a rat chronic constriction injury (CCI) model. By using the sciatic nerve CCI model, we studied the effect of anti-TNF-α treatment on recovery from hypersensitivity and TNFR expression in the dorsal root ganglion (DRG) and dorsal horn (DH). ⋯ Both treatments significantly diminished these increased levels. Treated animals that showed a ≥50% alleviation of pain exhibited a significantly reduced TNF R1/R2 mRNA ratio compared with treated animals that recovered less well. These results demonstrate that attenuation of TNFR expression is associated with recovery from nerve injury and suggest that this may be one of the working mechanisms of anti-TNF therapies.
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Acta Biochim. Biophys. Sin. (Shanghai) · Nov 2014
Circulating microRNA expression profile: a novel potential predictor for chronic nervous lesions.
The mechanisms of chronic neuropathic pain are not clear. Serum microRNAs (miRNAs) might show a special feature for chronic nervous lesions. However, little is known about the changes in circulating miRNAs for the neuropathic pain. ⋯ TargetScan was used to predict mRNA targets for these miRNAs, and the results showed that the transcripts with multiple predicted target sites belonged to neurologically important pathways. Bioinformatics analysis revealed that several target genes are related to the activation of cell signaling associated with nervous lesions. In this study, the changes to miRNA profiles in serum under neuropathic pain conditions were shown for the first time, suggesting that circulating miRNAs profile in serum is a potential predictor for neuropathic pain.
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Despite many advances, our understanding of the involvement of prodynorphin systems in the development of neuropathic pain is not fully understood. Recent studies suggest an important role of neuro-glial interactions in the dynorphin effects associated with neuropathic pain conditions. Our studies show that minocycline reduced prodynorphin mRNA levels that were previously elevated in the spinal and/or dorsal root ganglia (DRG) following sciatic nerve injury. ⋯ These results suggest an important role of these proinflammatory cytokines in the development of the neurotoxic effects of dynorphin. Similar to minocycline, a selective inhibitor of MMP-9 (MMP-9 levels are reduced by minocycline) exerts an analgesic effect in behavioral studies, and its administration prevents the occurrence of flaccid paralysis caused by high-dose dynorphin administration (15 nmol). In conclusion, our results underline the importance of neuro-glial interactions as evidenced by the involvement of IL-1β and IL-6 and the minocycline effect in dynorphin-induced toxicity, which suggests that drugs that alter the prodynorphin system could be used to better control neuropathic pain.