Pain
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Observational Study
Development and Validation of a New Self-Report Measure of Pain Behaviors.
Pain behaviors that are maintained beyond the acute stage after injury can contribute to subsequent psychosocial and physical disability. Critical to the study of pain behaviors is the availability of psychometrically sound pain behavior measures. In this study we developed a self-report measure of pain behaviors, the Pain Behaviors Self Report (PaB-SR). ⋯ Scores on the PaB-SR were found to be measurement invariant with respect to clinical condition. PaB-SR scores, observer reports, and the videotaped protocol yielded distinct, but convergent views of pain behavior, supporting the validity of the new measure. The PaB-SR is expected to be of substantial utility to researchers wishing to explore the relationship between pain behaviors and constructs such as pain intensity, pain interference, and disability.
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G-protein coupled inwardly rectifying potassium (GIRK) channels are effectors determining degree of analgesia experienced upon opioid receptor activation by endogenous and exogenous opioids. The impact of GIRK-related genetic variation on human pain responses has received little research attention. We used a tag single nucleotide polymorphism (SNP) approach to comprehensively examine pain-related effects of KCNJ3 (GIRK1) and KCNJ6 (GIRK2) gene variation. ⋯ A continuous GIRK Related Risk Score (GRRS) was derived in the primary sample to summarize each individual's number of KCNJ6 "pain risk" alleles. This GRRS was applied to the replication sample, which revealed significant associations (P < .05) between higher GRRS values and lower acute pain tolerance and higher CLBP intensity and unpleasantness. Results suggest further exploration of the impact of KCNJ6 genetic variation on pain outcomes is warranted.
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Anti-nerve growth factor (anti-NGF) treatment is analgesic in chronic inflammatory pain conditions without reducing inflammation. Hypothesizing that ongoing pain induced by inflammatory mediators is increased by long term sensitization of nociceptors, we combined the non-inflammatory NGF-sensitization model with an inflammatory ultraviolet-B (UV-B) model in human volunteers. UV-B irradiation of the skin presensitized with NGF 3 weeks before intensified the pre-existing NGF hyperalgesia during the inflammatory phase of UV-B and caused spontaneous pain in about 70% of the subjects. ⋯ Hyperalgesia and spontaneous pain coexisted in NGF/UV-B treated skin but did not significantly correlate (r < -0.1 at day 1 and r < 0.2 at day 3). We conclude that NGF can sensitize nociceptive endings such that inflammatory mediators may cause sufficient excitation to provoke spontaneous pain. Our results suggest that neuronal sensitization and level of inflammation represent independent therapeutic targets in chronic inflammatory pain conditions.
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Treating bone cancer pain poses a major clinical challenge, and the mechanisms underlying bone cancer pain remain elusive. EphrinB-EphB receptor signaling may contribute to bone cancer pain through N-methyl-d-aspartate receptor neuronal mechanisms. Here, we report that ephrinB-EphB signaling may also act through a Toll-like receptor 4 (TLR4)-glial cell mechanism in the spinal cord. ⋯ Intrathecal administration of an exogenous EphB1 receptor activator, ephrinB2-Fc, increased the expression of TLR4 and the levels of IL-1β and TNF-α, activated astrocytes and microglial cells, and induced thermal hypersensitivity. These ephrinB2-Fc-induced alterations were suppressed by spinal knockdown of TLR4. This study suggests that TLR4 may be a potential target for preventing or reversing bone cancer pain and other similar painful processes mediated by ephrinB-EphB receptor signaling.