Pain
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Although the behavioral response to pain is complex and involves supraspinal processes, assessment of pain symptoms in animal models still mainly relies on reflex-based nociceptive tests, which do not account for the affective-motivational nor cognitive components of pain. We introduce a double avoidance place preference paradigm, an integrated testing procedure in freely moving rats that relies on the conflict between the avoidance of a dark compartment in which a thermal ramp is activated, and the escape towards an aversive brightly lit compartment. We were able to differentiate the first nociceptive threshold from the temperature of definitive escape from the dark compartment, conveying information on the adaptive behavior of animals. ⋯ In animals exhibiting hyperalgesia following intraplantar complete Freund adjuvant injection, escape thresholds were significantly higher than that of control animals, hinting at a maladaptive affective-motivational response to noxious stimulation. However, in cuff animals, we failed to reveal any hot nociceptive hypersensitivity, but animals exhibited a strong adaptive response to cold simulation upon reexposure. Overall, the proposed paradigm allows for an integrated cortical response leading to a proactive avoidance behavior, while fully complying with ethical standards in animal experimentation.
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Children with Christianson syndrome (CS), an X-linked neurodevelopmental disorder caused by loss-of-function mutations in the alkali cation/proton exchanger SLC9A6/NHE6, display severe cognitive impairments, mutism, and sensory abnormalities such as hyposensitivity to pain. However, it is unclear whether these children display other sensory abnormalities and whether their pain hyposensitivity is the result of an elevated pain threshold or a complete insensitivity to pain. To better characterize the sensory abnormalities in this disorder, we used a combination of a mouse model of CS and pain questionnaires directed at nonverbal patients with CS. ⋯ Surprisingly, CS mice also displayed aversive reactions to innocuous stimuli, which prompted us to examine whether such reactions were also present in children with CS. Indeed, the results from the PSQ revealed that 30% to 50% of these patients showed an aversive response to normally innocuous stimuli like light touch and gusts of air. Our results demonstrate that children with CS have aversive reactions to innocuous stimuli and are hyposensitive to painful stimuli, the latter making them at risk for developing complications from unreported injuries.
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The objective of this study was to assess the frequency of IgG autoantibodies in patients with fibromyalgia syndrome (FMS), to characterize their binding to dorsal root ganglion (DRG) neurons and glial cells, and to assess whether specific DRG binding patterns correlate with clinical symptoms. Sera of a cohort of 184 patients with FMS and 55 control sera were used to test binding of patient IgG on rat DRG sections. ELISA, Western blot, and preadsorption tests were used to search for potential target antigens. ⋯ Current pain intensity correlated positively with IgG binding to FABP7 immunoreactive structures, and burning pain was associated with binding to transient receptor potential vanilloid 1 immunoreactive neurons. Specific antibody detection revealed 13 of 68 sera positive for anti-citrullinated peptide antibodies, 9 of 68 positive for SOX1 antibodies, 7 of 68 positive for antibodies against the serotonin receptor 5HT1AR, and 3 of 68 positive for fibroblast growth factor 3 antibodies. Our findings support the notion of an immune activation in a subgroup of patients with FMS.
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Spine-related neck-arm pain is heterogeneous and may present on a spectrum between nociceptive and neuropathic pain. A recently developed mechanism-based clinical framework for spine-related pain distinguishes between spinally referred pain without neurological deficits (somatic referred pain, heightened nerve mechanosensitivity, radicular pain), with neurological deficits (radiculopathy), and mixed-pain presentations. This study investigated differences in somatosensory and clinical profiles of patients with unilateral spine-related neck-arm pain grouped according to the clinical framework. ⋯ Symptom descriptors, such as burning (P < 0.031), tingling (P < 0.018), pins and needles (P < 0.031), numbness (P < 0.016), spontaneous pain (P < 0.001), and electric pain/shock (P < 0.026) were more common in the radicular/radiculopathy groups compared with the somatic/mechanosensitivity groups. There were no differences in psychosocial parameters between the groups. The phenotypic profiles support the construct of the clinical examination and patient classification and its application in clinical practice according to a clinical framework for spine-related pain.