Articles: hyperalgesia.
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In animals, decades of research have shown that serotonin (5-HT) is involved in endogenous pain inhibition systems, which are deficient in chronic pain disorders such as fibromyalgia (FM). In humans, there is preliminary evidence showing that 5-HT is involved in the FM pathophysiology. In the current endophenotyping study, we sought to investigate, for the first time in humans, the relationships between the serotonin transporter promoter region (5-HTTLPR) polymorphism and experimentally-induced pain perception/inhibition in healthy controls (HC) and FM patients. ⋯ Our results further confirm that FM is associated with thermal hyperalgesia and deficient DNIC. However, we found no evidence showing that the 5-HTTLPR polymorphism influences pain perception and DNIC. Potential reasons for this negative result will be discussed. Further endophenotyping studies of 5-HT-related gene polymorphisms are required to ascertain the potential relationships between 5-HT and human pain perception/inhibition.
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Withdrawal from analgesic and addictive substances such as opioids or ethanol is associated with increased sensitivity to sensory stimulation in animal models. Here, we investigated perception of innocuous and noxious thermal or electric stimuli applied to the left hand or sternum in 30 male patients undergoing withdrawal from alcohol, 30 male abstained alcoholics and matched controls. The alcohol withdrawal scale and the Banger score were obtained to estimate the severity of withdrawal. ⋯ No differences were found between patients of the abstained group and control subjects for any pain parameter. In conclusion, we demonstrate withdrawal-induced hyperalgesia upon thermal stimulation in patients. Since the influence of affective symptoms on pain perception during withdrawal is remarkable, we assume that peripheral and central mechanisms might account for this finding, which should be assessed in detail in future studies.
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Arthritis care & research · Aug 2010
Pressure pain sensitivity topographical maps reveal bilateral hyperalgesia of the hands in patients with unilateral carpal tunnel syndrome.
To assess topographical pressure pain sensitivity maps of the hand in patients with unilateral carpal tunnel syndrome (CTS) as compared with healthy subjects. ⋯ Our findings revealed bilateral generalized pressure pain hyperalgesia in unilateral CTS because lower PPT levels were found in all of the points. The pressure pain hyperalgesia was not uniformly distributed since PPTs were lower in points over the proximal phalanx of the fingers and the thenar eminency as compared with those points located over the distal phalanx of the fingers. The decrease in PPT levels was associated with the intensity and the duration of the pain symptoms, supporting a role of both peripheral and central sensitization mechanisms in this pain condition.
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Brain-derived neurotrophic factor (BDNF) and its cognate receptor, the tyrosine kinase B (TrkB), are normally expressed in neurons and implicated in multiple pathological conditions. Brain-derived neurotrophic factor is produced in the central nervous system microglia in response to noxious stimuli and appear to potentiate central sensitization. Resiniferatoxin (RTX) is an excitotoxic agonist of the vanilloid receptor 1 (VR1), a cation channel protein considered an integrator for nociception. Resiniferatoxin, administered into the dorsal root ganglia (DRG), selectively eliminates the VR1-positive neurons and improves tactile allodynia in a neuropathic pain rat model. ⋯ Resiniferatoxin injection in the DRG of neuropathic rats upregulates BDNF expression in the same pattern as in the large-size neurons of non-neuropathic rats. Therefore, BDNF upregulation may have pain suppressive effects. These effects are likely mediated by TrkB.
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Chronic stressful events induce biochemical, physiological and psychological changes, resulting in stress-related neuropsychiatric disorders, such as anxiety or depression. Using repeated social defeat as a stressful event model, we show that this preclinical paradigm induces a transient increase in the expression of the genes encoding the pro-inflammatory molecules iNOS and COX-2. We provide the first demonstration that chronic stress affects spinal plasticity through a mechanism involving local neuroinflammation. ⋯ The present study highlights the adverse effects of chronic stress on spinal neuroinflammation triggering sensory hypersensitivity. Exploration of this phenomenon points out the divergence between pain sensitivity and anxiety-induced hyperalgesia, which is in agreement with clinical observations. Altogether, these data open up new perspectives for clinical research devoted to the evaluation and treatment of pain in anxio-depressive patients.