Pain
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Partial nerve injury leads to peripheral neuropathic pain. This injury results in conducting/uninterrupted (also called uninjured)sensory fibres, conducting through the damaged nerve alongside axotomised/degenerating fibres. In rats seven days after L5 spinal nerve axotomy (SNA) or modified-SNA (added loose-ligation of L4 spinal nerve with neuroinflammation-inducing chromic-gut),we investigated (a) neuropathic pain behaviours and (b) electrophysiological changes in conducting/uninterrupted L4 dorsal root ganglion (DRG) neurons with receptive fields (called: L4-receptive-field-neurons). ⋯ We recorded intracellularly in vivo from normal L4/L5 DRG neurons and ipsilateral L4-receptive-field-neurons. After SNA or modified-SNA, L4-receptive-field-neurons showed the following: (a) increased percentages of C-, Aδ-, and Aβ-nociceptors and cutaneous Aα/β-low-thresholdmechanoreceptors with ongoing/spontaneous firing; (b) spontaneous firing in C-nociceptors that originated peripherally; this was ata faster rate in modified-SNA than SNA; (c) decreased electricalthresholds in A-nociceptors after SNA; (d) hyperpolarised membrane potentials in A-nociceptors and Aα/-low-thresholdmechanoreceptors after SNA, but not C-nociceptors; (e) decreased somatic action potential rise times in C- and A-nociceptors, not Aα/β-low-threshold-mechanoreceptors. We suggest that these changes in subtypes of conducting/uninterrupted neurons after partial nerve injury contribute to the different aspects of neuropathic pain as follows: spontaneous firing in nociceptors to ongoing/spontaneous pain; spontaneous firing in Aα/β-low-threshold-mechanoreceptors to dysesthesias/paresthesias; and lowered A-nociceptor electrical thresholds to A-nociceptor sensitization,and greater evoked pain [corrected].
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The importance of willingness to adopt a self-management approach to chronic pain has been demonstrated in the context of cognitive-behaviorally oriented interdisciplinary pain treatment programs for adults, both as a treatment outcome and as a process that facilitates functional improvements. Willingness to self-manage pain has not been studied in pediatric interdisciplinary pain treatment settings. Study aims were (1) to investigate willingness to self-manage pain among children and parents undergoing intensive interdisciplinary pain treatment and (2) to determine whether increased willingness to self-manage pain influenced functional treatment outcomes. ⋯ Increases in parents' readiness to adopt a pain self-management approach were associated with changes in parent-reported fear of pain but not with other child outcomes. Few associations emerged between pretreatment willingness to self-manage pain and posttreatment outcomes. Findings suggest that interdisciplinary pediatric pain rehabilitation may facilitate increased willingness to self-manage pain, which is associated with improvements in function and psychological well-being.
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Many acute stressors reduce pain, a phenomenon called stress-induced antinociception (SIA). Stress also is associated with increased scratching in chronic itch conditions. We investigated effects of acute stressors on facial itch and pain using a recently introduced rat model. ⋯ W-SIA tended to equalize scratching and swiping elicited by 5-HT and AITC compared with no-swim controls, suggesting altered itch and pain processing. Exercise (wheel-running), novelty, cold exposure, and fear (shaker table), key components of swim stress, differentially affected tail-flick latencies and 5-HT-evoked swiping and scratching behavior. Thus, itch and pain can be simultaneously suppressed by a combination of acute stress-related factors via an opioid-independent mechanism.