Pain
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Comparative Study
Effects of mood on pain responses and pain tolerance: an experimental study in chronic back pain patients.
Although chronic pain and depression commonly co-occur, causal relationships have yet to be established. A reciprocal relationship, with depression increasing pain and vice versa, is most frequently suggested, but experimental evidence is needed to validate such a view. The most straightforward approach would be a demonstration that increasing or decreasing depressed mood predictably modifies pain responses. ⋯ Results indicate that the induction of depressed mood resulted in significantly higher pain ratings at rest and lower pain tolerance, whilst induced happy mood resulted in significantly lower pain ratings at rest and greater pain tolerance. Correlations between changes in mood on the one hand and changes in pain response and pain tolerance on the other hand were consistent with these findings. It is concluded that, in chronic back pain patients, experimentally induced negative mood increases self-reported pain and decreases tolerance for a pain-relevant task, with positive mood having the opposite effect.
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Comparative Study
Sensitization of primary afferents to mechanical and heat stimuli after incision in a novel in vitro mouse glabrous skin-nerve preparation.
In this study, we recorded activity from afferent fibers innervating the mouse plantar skin, the same region evaluated in pain behavior experiments. We compared responses of afferents from incised and unincised hind paw skin. The plantar skin together with attached medial and lateral plantar nerves was dissected until they could be completely removed intact and placed in an organ bath chamber continuously perfused with oxygenated Kreb's solution with the temperature maintained at 32 degrees C. ⋯ Few fibers were excited by cooling. Heat sensitization of primary afferents was more prominent when activities of unclassified afferents are included. The preparation allows us to study afferent function of the same tissue that is examined for in vivo pain behavior assays in mice.
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Comparative Study
The effects of parental presence upon the facial expression of pain: the moderating role of child pain catastrophizing.
This experiment investigated the effects of child catastrophic thinking and parental presence on the facial expressions of children when experiencing pain. School children experienced pressure pain in either one of two conditions: (1) when observed by a parent (n=53 children and their parent), or (2) when observed by an adult stranger (n=31 children). ⋯ Children who have frequent catastrophic thoughts expressed high pain regardless of who they believed was observing them. Results are discussed in terms of the social consequences of pain catastrophizing, and the variables contributing to the expression or suppression of pain display in children and its impact upon others.
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Randomized Controlled Trial Comparative Study
Effects of progressive muscle relaxation training on nociceptive flexion reflex threshold in healthy young adults: a randomized trial.
Although prior studies have demonstrated effects of progressive muscle relaxation (PMR) in reducing self-reported pain, no laboratory studies have examined the effects of PMR on objective indicators of descending modulation of nociception. This randomized controlled study utilized the nociceptive flexion reflex (NFR) to evaluate nociceptive responding among 55 college-age men and women (mean age=19.4+/-1.2 years). Participants completed laboratory assessments of NFR threshold and questionnaires evaluating pain and stress. ⋯ Ratings of pain did not change during the study, but PMR participants reported decreased stress following the PMR intervention. This is the first study with a randomized no-treatment control group demonstrating the effect of a brief PMR protocol on descending inhibition of nociception. Results support the efficacy of PMR in reducing nociceptive response and provide further evidence of the utility of behavioral pain management strategies.
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Comparative Study
Principle components analysis of pain thresholds to thermal, electrical, and mechanical stimuli suggests a predominant common source of variance.
We addressed the question whether pain thresholds to different stimuli measure independent aspects of pain or one common phenomenon. In the first case, different stimuli are required to completely characterize a subject's pain sensitivity. In the second case, different stimuli are redundant and can be used to calculate composite scores across pain modalities. ⋯ Only minor variance components, each explaining <14% of the total variance, indicated a distinction of pain stimuli. There, a pattern of similarities and dissimilarities emerged agreeing with known distinct mechanisms of nociceptive responses to different stimuli. We conclude that characterizing a person as being generally stoical or complaining to any painful stimulus appears to be justified at least at pain threshold level.