Pain
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Calcitonin gene-related peptide (CGRP) is a 37-amino acid peptide found primarily in the C and Aδ sensory fibers arising from the dorsal root and trigeminal ganglia, as well as the central nervous system. Calcitonin gene-related peptide was found to play important roles in cardiovascular, digestive, and sensory functions. Although the vasodilatory properties of CGRP are well documented, its somatosensory function regarding modulation of neuronal sensitization and of enhanced pain has received considerable attention recently. ⋯ Recent successful clinical studies have shown that blocking the function of CGRP can alleviate migraine. However, the mechanisms through which CGRP may contribute to migraine are still not fully understood. We reviewed the role of CGRP in primary afferents, the dorsal root ganglion, and in the trigeminal system as well as its role in peripheral and central sensitization and its potential contribution to pain processing and to migraine.
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Posttraumatic stress disorder (PTSD) symptoms and pain after traumatic events such as motor vehicle collision (MVC) have been proposed to be mutually promoting. We performed a prospective multicenter study that enrolled 948 individuals who presented to the emergency department within 24 hours of MVC and were discharged home after evaluation. Follow-up evaluations were completed 6 weeks, 6 months, and 1 year after MVC. ⋯ In addition, path analysis results supported the hypothesis that one or more PTSD symptom clusters had an influence on axial pain outcomes throughout the year after MVC, with hyperarousal symptoms most influencing axial pain persistence in the initial months after MVC. The influence of hyperarousal symptoms on pain persistence was only present among individuals with genetic vulnerability to stress-induced pain, suggesting specific mechanisms by which hyperarousal symptoms may lead to hyperalgesia and allodynia. Further studies are needed to better understand the specific mechanisms by which pain and PTSD symptoms enhance one another after trauma, and how such mechanisms vary among specific patient subgroups, to better inform the development of secondary preventive interventions.
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Sensitization is a form of implicit learning produced by the exposure to a harmful stimulus. In humans and other mammals, sensitization after skin injury increases the responsiveness of peripheral nociceptors and enhances the synaptic transmission of nociceptive input in the central nervous system. ⋯ Whereas mechanical hyperalgesia was present both 20 and 45 minutes after HFS, the enhanced responsiveness to visual stimuli was present only 20 minutes after HFS. Taken together, our results indicate that sensitization involves both nociceptive-specific and multimodal mechanisms, having distinct time courses.
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This study examined outcomes and predictors of different types of responses to child pain used by caregivers of youth with chronic disease. Sixty-six children and adolescents (ages 7-18) with juvenile idiopathic arthritis answered questions about pain, pain interference in activities, and mood on a smartphone three times per day for one month, while a caregiver contemporaneously answered questions about their own mood and use of protecting, monitoring, minimizing, or distracting responses to their child's pain. Multilevel models were used to evaluate (a) how a child's pain and pain interference changes after a caregiver uses different types of pain responses; (b) the extent to which caregiver responses to pain vary across days; and (c) whether variability in caregiver responses to pain is predicted by changes in child pain characteristics, child mood, and/or caregiver mood. ⋯ Caregiver pain responses varied considerably across days, with caregivers responding with more protecting and monitoring responses and fewer minimizing responses at moments when their child reported high levels of pain unpleasantness and pain interference. Caregivers also were found to respond with fewer protective responses at moments when they themselves were in a more positive mood. Implications for clinical recommendations and future studies are discussed.