European journal of pain : EJP
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Peripheral nerve injury leading to neuropathic pain induces the upregulation of interleukin (IL)-6 and microglial CX3CR1 expression, and activation of p38 mitogen-activated protein kinase (MAPK) in the spinal cord. Here, we investigated whether IL-6 regulates CX3CR1 expression through p38 MAPK activation in the spinal cord in rats with chronic constriction injury (CCI) of the sciatic nerve. Similar temporal changes in the expression of IL-6, phosphorylated p38 MAPK and CX3CR1 were observed following CCI. ⋯ Furthermore, treatment with the p38 MAPK-specific inhibitor, SB203580, suppressed the increase in CX3CR1 expression induced by CCI or rrIL-6 treatment. Finally, blocking CX3CR1 or p38 MAPK activation prevented the development of mechanical allodynia and thermal hyperalgesia induced by CCI or rrIL-6 treatment. These results suggest a new mechanism of neuropathic pain, in which IL-6 induces microglial CX3CR1 expression in the spinal cord through p38 MAPK activation, enhancing the responsiveness of microglia to fractalkine in the spinal cord, thus playing an important role in neuropathic pain after peripheral nerve injury.
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Painful diabetic neuropathy may be due to impairments in descending modulation of nociceptive transmission at the spinal cord. In the present study, streptozotocin diabetic rats (STZ rats) with neuropathic symptoms (mechanical hypersensitivity) were used to perform a time-course evaluation of neuronal activity at the spinal dorsal horn and at the periaqueductal grey matter (PAG), a major brainstem area of pain modulation. The expression of Fos protein, a marker of nociceptive activation, progressively increased at the spinal dorsal horn at 4 and 10 weeks. ⋯ The present study shows that diabetic neuropathy is accompanied by a progressive increase of the spontaneous neuronal activity at the spinal cord. Changes in descending modulation of nociceptive transmission from the PAG are likely to occur during diabetic neuropathy, probably with exacerbation of facilitatory actions. The effects of gabapentin in reversing the behavioural signs of diabetic neuropathy and neuronal hyperactivity in the spinal cord and PAG reinforce the central causes of diabetic neuropathy and point to the central targets of the drug.
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Chronic neuropathic pain is often associated with conditions such as depression and anxiety and strongly affects daily functioning and overall quality of life. It is argued, therefore, that psychosocial interventions should be added to traditional biomedical interventions. This systematic review evaluates the effectiveness of cognitive and behavioral interventions for the management of chronic neuropathic pain. ⋯ This is the first systematic review that has evaluated the effectiveness of cognitive and behavioral techniques for the management of chronic neuropathic pain. Given the limited methodological quality, no informative conclusions can be drawn with respect to the study objective. However, this review does provide insight into the difficulties of this specific area, the need for a clear and widely accepted definition of neuropathic pain and the need for standardized multidimensional measurement instruments.
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Recent developments within CBT have emphasized acceptance rather than control of pain and distress in treatments aimed at improving functioning and life quality, but there is still a lack of reliable and valid instruments to assess relevant processes in such interventions. The Psychological Inflexibility in Pain Scale (PIPS) was developed to assess target variables in exposure and acceptance oriented treatments. A preliminary validation study resulted in a two-factor solution with subscales for avoidance and cognitive fusion related to pain, showing satisfactory psychometric properties. ⋯ Notably, hierarchical regression analyses illustrated that PIPS explained more variance than TSK in pain, disability, life satisfaction and depression. Furthermore, PIPS was found to mediate the relationship between e.g. pain and disability, suggesting the usefulness of PIPS as a process measure in treatments of people with chronic pain. Thus, it is argued that this 12-item version of PIPS may be used to explore the importance of psychological in/flexibility in chronic pain and to analyse processes of change in exposure based interventions, as well as for clinicians in tailoring interventions for patients with chronic debilitating pain.
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In animals, decades of research have shown that serotonin (5-HT) is involved in endogenous pain inhibition systems, which are deficient in chronic pain disorders such as fibromyalgia (FM). In humans, there is preliminary evidence showing that 5-HT is involved in the FM pathophysiology. In the current endophenotyping study, we sought to investigate, for the first time in humans, the relationships between the serotonin transporter promoter region (5-HTTLPR) polymorphism and experimentally-induced pain perception/inhibition in healthy controls (HC) and FM patients. ⋯ Our results further confirm that FM is associated with thermal hyperalgesia and deficient DNIC. However, we found no evidence showing that the 5-HTTLPR polymorphism influences pain perception and DNIC. Potential reasons for this negative result will be discussed. Further endophenotyping studies of 5-HT-related gene polymorphisms are required to ascertain the potential relationships between 5-HT and human pain perception/inhibition.