Pain
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Comorbidity of pain and posttraumatic stress disorder is well recognized, but the reason for this association is unclear. This study investigated the direction of the relationship between pain and traumatic stress and the role that pain-related fear plays, for patients with acute whiplash-associated disorder. Participants (n = 99) used an electronic diary to record hourly ratings of pain, traumatic stress, and fear of pain (FOP) symptoms over a day. ⋯ Differences between this study and others that reported mutual maintenance can be understood in terms of different stages of whiplash-associated disorder and different intervals between repeated measurements. Traumatic stress may affect pain over longer time intervals than measured in this study. Future research could explore how relationships between traumatic stress symptoms, pain, and FOP change over time, and whether previous experiences of traumatic stress influence these relationships.
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Migraine is a debilitating condition; however, the pharmacological effects on central nervous system networks after successful therapy are poorly understood. Defining this neurocircuitry is critical to our understanding of the disorder and for the development of antimigraine drugs. ⋯ Whole-brain analysis yielded significant between-group (inflammatory soup vs synthetic interstitial fluid) alterations in functional connectivity across the cerebellar, default mode, basal ganglia, autonomic, and salience networks. These results demonstrate the large-scale antimigraine effects of sumatriptan-naproxen co-administration after dural sensitization.
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Irritable bowel syndrome (IBS) is a visceral pain condition with psychological comorbidity. Brain imaging studies in IBS demonstrate altered function in anterior insula (aINS), a key hub for integration of interoceptive, affective, and cognitive processes. However, alterations in aINS excitatory and inhibitory neurotransmission as putative biochemical underpinnings of these functional changes remain elusive. ⋯ Our findings provide first evidence for reduced excitatory but unaltered inhibitory neurotransmitter levels in aINS in IBS. The results also indicate a functional lateralization of aINS with a stronger involvement of the right hemisphere in perception of abdominal pain and of the left aINS in cognitive pain regulation. Our findings suggest that glutaminergic deficiency may play a role in pain processing in IBS.
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Inflammatory pain hypersensitivity is associated with activation of primary afferent neurons. This study investigated the existence of the inflammasome in dorsal root ganglion (DRG) and the functional significance in the development of inflammatory pain hypersensitivity. Tissue inflammation was induced in male C57BL/6 mice with complete Freund's adjuvant (CFA) or ceramide injection into the hind paw. ⋯ NLRP2 siRNA inhibited ceramide-induced pain hypersensitivity. These results confirmed the existence of NLRP2 inflammasome in DRG neurons. Activation of the NLRP2 inflammasome leads to activation of DRG neurons and subsequent development of pain hypersensitivity in various types of tissue inflammation.