Pain
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Fibromyalgia is a prevalent and burdensome disorder characterized by chronic widespread pain and complex comorbid symptoms. To develop better treatments for pain-centered fibromyalgia symptoms, there is still a need for animal models which mimic the features of fibromyalgia patients. In the present study, we have established a fibromyalgia animal model by utilizing a never-before-published pharmacological effect of reserpine. ⋯ Pregabalin, duloxetine, and pramipexole significantly attenuated the reserpine-induced decrease in muscle pressure threshold, but diclofenac did not. The validity of the use of this reserpinized animal as a fibromyalgia model is demonstrated from three different aspects, i.e., face validity (manifestation of chronic pain and comorbid symptoms), construct validity (dysfunction of biogenic amine-mediated central nervous system pain control is involved), and predictive validity (similar responses to treatments used in fibromyalgia patients). This animal model is expected to contribute to the better understanding of fibromyalgia pathophysiology and the evaluation of drugs, especially those which would activate biogenic amine system.
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Placebo has been shown to be a powerful analgesic with corresponding reduction in the activation of the pain matrix in the brain. However it is not clear whether the placebo response is reproducible within individuals and what role personality traits might play in predicting it. We induced placebo analgesia by conditioning subjects to expect pain reduction following a sham-treatment in the guise of a local anaesthetic cream applied to one arm. ⋯ A regression model was used to statistically define a placebo responder in terms of personality scores. High dispositional optimism and low state anxiety were found to be significant predictors of placebo response. We suggest that repeated placebo responders are high in dispositional optimism and having a placebo response in the first session causes a drop in state anxiety at the beginning of the repeat session.
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Investigated was the relationship between pain catastrophizing and pain intensity in adolescents suffering from chronic pain (n = 38) and the extent to which they expressed communicative pain and pain-related protective behaviours. Adolescents were observed on video performing a 2-Min Walk Test (2MWT). Behaviours were coded on videotape. ⋯ Pain-related protective behaviours did not vary with the adolescents' level of pain catastrophizing, but varied with pain intensity. The findings corroborate the functional distinctiveness of different types of pain behaviours. The results are discussed in terms of the processes linking (1) catastrophizing to communicative pain behaviours and (2) pain to pain-related protective behaviours.
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Experimental determination of pain sensitivity has received increasing attention because of emerging clinical applications (including prediction of postoperative pain and treatment response) and scientific implications (e.g. it has been proposed that above-average pain sensitivity is a risk factor for the development of chronic pain disorders). However, the use of experimental pain sensitivity assessment on a broad scale is hampered by its requirements on time, equipment and human resources and the fact that it is painful for the tested subject. Alternatives to experimental pain testing are currently lacking. ⋯ PSQ scores were significantly correlated to experimental pain intensity ratings (r = 0.56, p < 0.001) but not to pain thresholds (r = 0.03). Prediction of experimental pain intensity ratings by the PSQ was better than by pain-associated psychological factors (pain catastrophizing, depression, anxiety). This shows that the PSQ may be a simple alternative to experimental pain intensity rating procedures in healthy subjects and makes the PSQ a highly promising tool for clinical and experimental pain research.
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Patients with neuropathic pain syndromes are heterogeneous. They present with a variety of sensory symptoms and pain qualities. The knowledge of these data and etiology-specific differences is important to optimize clinical trial design and to develop more effective drugs. ⋯ All subgroups occur in relevant numbers in both entities but the frequencies differ between PHN and DPN. Since sensory symptoms likely translate into pain-generating mechanisms enrichment for potential treatment responders might be possible in clinical trials by assessing the sensory profiles. Patient-Reported Outcomes can be used to obtain a precise sensory characterization of each patient.