Pain
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Recent functional brain connectivity studies have contributed to our understanding of the neurocircuitry supporting pain perception. However, evoked-pain connectivity studies have employed cutaneous and/or brief stimuli, which induce sensations that differ appreciably from the clinical pain experience. Sustained myofascial pain evoked by pressure cuff affords an excellent opportunity to evaluate functional connectivity change to more clinically relevant sustained deep-tissue pain. ⋯ Moreover, greater connectivity during pain between contralateral S1/M1 and posterior insula, thalamus, putamen, and amygdala was associated with lower cuff pressures needed to reach the targeted pain sensation. These results demonstrate that sustained pain disrupts resting S1/M1 connectivity by shifting it to a network known to process stimulus salience. Furthermore, increased connectivity between S1/M1 and both sensory and affective processing areas may be an important contribution to interindividual differences in pain sensitivity.
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In this prospective cohort study we aimed to describe the natural course of acute neck and low back pain in a general population of Norway. We screened 9056 subjects aged 20-67 years who participated in a general health survey for a new episode of neck or low back pain the previous month. The screening identified 219 subjects who formed the cohort for this study. ⋯ Only 1 in 5 sought health care for their complaints. Still, the course of pain was comparable to effect sizes reported in interventional studies. This study thus contributes natural course reference data for comparisons of pain outcome in clinical trials and practice.
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The perception of pain is determined by a combination of genetic, neurobiological, cultural, and emotional factors. Recent studies have demonstrated an association between specific genotypes and pain perception. Particular focus has been given to the triallelic polymorphism in the promoter region of the serotonin transporter gene in relation to pain perception. ⋯ However, in participants with a high expression of the serotonin transporter protein, conditioning with negative pictures increased pain intensity and positive pictures decreased pain intensity when compared with neutral pictures. In contrast, there were no significant effects of the pictures on pain perception in participants with either intermediate or low expression of the protein. These results suggest that polymorphisms in the serotonin transporter gene play an important role in emotions modulation of muscle pain.
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Randomized Controlled Trial
Oxycodone alters temporal summation but not conditioned pain modulation: preclinical findings and possible relations to mechanisms of opioid analgesia.
Opioid analgesia is mediated primarily by modulating (inhibiting and enhancing) pain mechanisms at the spinal and supraspinal levels. Advanced psychophysical paradigms of temporal summation (TS) and conditioned pain modulation (CPM) likely represent pain mechanisms at both levels. Therefore, the study of opioid effects on TS and CPM can shed light on their analgesic mechanisms in humans. ⋯ In contrast, no significant effects of either oxycodone (F=0.871, P=.458) or placebo (F=2.086, P=.106) on the magnitude of CPM were found. These results suggest that under the current experimental conditions, oxycodone exerted spinal, rather than supraspinal, analgesic effects. Furthermore, compared with CPM, TS seems more suitable for studying the mechanisms of opioid analgesia in humans.