Pain
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Comparative Study
A longitudinal study on the predictive validity of the fear-avoidance model in low back pain.
Recently, fear-avoidance models have been quite influential in understanding the transition from acute to chronic low back pain (LBP). Not only has pain-related fear been found to be associated with disability and increased pain severity, but also treatment focused at reducing pain-related fear has shown to successfully reduce disability levels. In spite of these developments, there is still a lack in well-designed prospective studies examining the role of pain-related fear in acute back pain. ⋯ A backward ordinal regression analysis showed previous LBP history and pain intensity to be the most important predictors of end of study GCPS. Of the fear-avoidance model variables, only negative affect added to this model. Our results do not really support the longitudinal validity of the fear-avoidance model, but they do feed the discussion on the role of pain-related fear in early stages of LBP.
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Comparative Study
Peripheral axonal injury results in reduced mu opioid receptor pre- and post-synaptic action in the spinal cord.
In both the spared nerve injury (SNI) and spinal nerve ligation (SNL) rat peripheral neuropathic pain models the presynaptic inhibitory effect of the mu opioid receptor (MOR) agonist (DAMGO) on primary afferent-evoked excitatory postsynaptic currents (EPSCs) and miniature EPSCs in superficial dorsal horn neurons is substantially reduced, but only in those spinal cord segments innervated by injured primary afferents. The two nerve injury models also reduce the postsynaptic potassium channel opening action of DAMGO on lamina II spinal cord neurons, but again only in segments receiving injured afferent input. The inhibitory action of DAMGO on ERK (extracellular signal-regulated kinase) activation in dorsal horn neurons is also reduced in affected segments following nerve injury. ⋯ Decreased activation of MOR on injured primary afferent central terminals and the second order neurons they innervate may minimize any reduction by opioids of the spontaneous pain mediated by ectopic input from axotomized small diameter afferents. Retention of MOR expression and activity in nearby non-injured afferents will enable, however, an opioid-mediated reduction of stimulus-evoked and spontaneous pain carried by intact nociceptor afferents and we find that intrathecal DAMGO (1000 ng) reduces mechanical hypersensitivity in rats with SNL. Axotomy-induced changes in MOR may contribute to opioid- insensitive components of neuropathic pain while the absence of these changes in intact afferents may contribute to the opioid sensitive components.
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Comparative Study
Psychometric properties of the TSK-11: a shortened version of the Tampa Scale for Kinesiophobia.
The Tampa Scale for Kinesiophobia (TSK) is one of the most frequently employed measures for assessing pain-related fear in back pain patients. Despite its widespread use, there is relatively little data to support the psychometric properties of the English version of this scale. This study investigated the psychometric properties of the English version of the TSK in a sample of chronic low back pain patients. ⋯ In respect of specific cut-off scores, a reduction of at least four points on both measures maximised the likelihood of correctly identifying an important reduction in fear of movement. Overall, the TSK-11 possessed similar psychometric properties to the original TSK and offered the advantage of brevity. Further research is warranted to investigate the utility of the new instrument and the cut-off scores in a wider group of chronic pain patients in different clinical settings.
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We developed a mouse model of cancer pain to investigate its underlying mechanisms. SCC-7, squamous cell carcinoma (SCC) derived from C3H mice, was inoculated subcutaneously into either the plantar region or thigh in male C3H/Hej mice. Heat and mechanical sensitivity as well as spontaneous behavior were measured at the plantar surface of the ipsilateral hind paw after the inoculation. ⋯ Intraperitoneal administration of the competitive TRPV1 antagonist capsazepine inhibited hyperalgesia induced by tumor cell-inoculation in either plantar- or thigh-inoculated animals. This study indicated that inoculation of SCC resulted in spontaneous pain, heat hyperalgesia and mechanical allodynia. The altered expression of TRPV1 in the DRG may be involved in behavioral changes in this model.
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Randomized Controlled Trial Comparative Study Clinical Trial
Effects of intradermal foot and forearm capsaicin injections in normal and vulvodynia-afflicted women.
Cutaneous response to capsaicin has been used to assess central sensitization in pain research. This study compared the response to intradermal capsaicin in the forearm and foot of vulvar vestibulitis (vestibulodynia)-afflicted cases and controls. We hypothesized that cases will experience greater spontaneous pain, larger cutaneous areas of punctate hyperalgesia and dynamic allodynia, and greater vascular flow than controls. ⋯ VVS cases had higher resting pulse rates and lower resting systolic blood pressures than in controls. Conclusion. VVS patients show enhancement of post-capsaicin pain response extending far beyond the anatomic location of the primary complaint.