Pain
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The important role of operant learning in the development and maintenance of chronic pain is widely recognized. A specific type of reinforcement based on the reduction of painful stimulation when a person's perception changes in the desired direction has been termed intrinsic reinforcement of pain. In the present study, the role of intrinsic operant learning in chronic pain was tested in fibromyalgia (FM) patients with and without comorbid irritable bowel syndrome (IBS) compared with healthy persons. ⋯ Whereas healthy persons learned perceptual changes according the experimental protocol, both patient groups failed to show normal operant perceptual learning: FM patients without IBS demonstrated sensitization learning comparable to that in healthy persons, but unexpectedly these patients learned even more pronounced sensitization in the habituation learning condition, contradicting the experimental protocol; FM patients with IBS demonstrated neither learning of enhanced sensitization nor enhanced habituation; no signs of differential operant learning were observable. Thus, operant perceptual learning was impaired in FM patients; whether learning of both enhanced perceptual sensitization and habituation was impaired depended on the presence of comorbid IBS and could not be explained by other clinical characteristics of the patients such as pain threshold, duration of pain, depressive symptoms, or anxiety. While healthy participants learned sensitization and habituation according to an operant task, FM patients without IBS showed enhanced sensitization and FM with IBS no learning.
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Randomized Controlled Trial Clinical Trial
On the importance of placebo timing in rTMS studies for pain relief.
The efficacy of repetitive transcranial magnetic stimulation (rTMS) of the motor cortex for neuropathic pain relief is founded on double-blind studies versus placebo. In these studies, however, the analgesic effect of active interventions remained modest compared with the placebo effect. This observation led us to re-evaluate the intrinsic placebo action on pain relief according to the relative timing of active and sham rTMS interventions. ⋯ The fact that placebo effects could be enhanced by a previous rTMS with an analgesic effect as low as 10% suggests that a 30% pain decrease threshold in therapeutic trials may be too severe because smaller analgesic effects may have a clinical significance too. Sham rTMS induces significant analgesia only when preceded by a successful active stimulation. Such a placebo modulation is probably related to an unconscious conditioned learning.
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Randomized Controlled Trial
Long-term effects of routine morphine infusion in mechanically ventilated neonates on children's functioning: five-year follow-up of a randomized controlled trial.
Newborns on ventilatory support often receive morphine to induce analgesia. Animal experiments suggest that this may impair subsequent cognitive and behavioral development. There are sparse human data on long-term effects of neonatal morphine. ⋯ However, scores on one IQ subtest, "visual analysis," were significantly negatively related to having received morphine and to open-label morphine consumption the first 28 days. The finding of a significant effect of morphine on the "visual analysis" IQ subtest calls for follow-up at a later age focusing on the higher-order neurocognitive functions. Morphine received in the neonatal period has negative effects on the child's cognitive functioning at the age of 5 years which warrants follow-up at a later age.
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The development of new strategies for the treatment of acute pain requires the identification of novel nonopioid receptor targets. This study explored whether δ-subunit-containing GABA(A)Rs (δGABA(A)Rs) in neurons of the spinal cord dorsal horn generate a tonic inhibitory conductance in vitro and whether δGABA(A)R activity regulates acute nociception. Whole-cell recordings revealed that δGABA(A)Rs generate a tonic inhibitory conductance in cultured spinal neurons and lamina II neurons in spinal cord slices. ⋯ Surprisingly, THIP reduced the enhanced phase 2 response in Gabrd(-/-) mice. Together, these results suggest that δGABA(A)Rs in spinal neurons play a major physiological and pharmacological role in the regulation of acute nociception and central sensitization. Spinal δ-subunit-containing GABA(A) receptors were identified with electrophysiological methods and behavioral models as novel targets for the treatment of acute pain.
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Problems in diagnosing fibromyalgia syndrome (FM) among motor vehicle collision (MVC) patients with whiplash (WL) include the following: the predominance of tender points (TPs) in the neck/shoulder girdle region; the 3-month duration of widespread pain criterion; and, the stability of diagnosis. The present study examined the prevalence of FM in a cohort (N = 326) patients with persistent neck pain 3 months after WL injury who were enrolled in a treatment program. Physical examinations were performed at baseline and at the end of treatment. ⋯ In conclusion, present criteria used in determining FM may result in spuriously inflated rates of diagnosis among WL patients because of persistent localized tenderness after an MVC. Furthermore, the transient nature of FM "symptoms" among WL patients should be taken into account before making a final diagnosis. The present criteria used in determining fibromyalgia may result in spuriously inflated rates of diagnosis among whiplash patients because of persistent localized tenderness after motor vehicle collisions.