Pain
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Randomized Controlled Trial
Acupuncture induced changes of the pressure pain threshold are mediated by segmental inhibition - a randomized controlled trial.
Our aim was to distinguish between spinal and supraspinal mechanisms in the intact nervous system by comparing homosegmental and heterosegmental effects of electroacupuncture (EA) and manual acupuncture (MA) on sensory perception in healthy volunteers by means of quantitative sensory testing. Seventy-two healthy volunteers were randomly assigned to receive either MA or EA at SP 6, SP 9, GB 39, and ST 36 at the left leg or relaxed for 30 minutes (control group [CG]). Blinded examiners assessed 13 sensory modalities (thermal and mechanical detection and pain thresholds) at the upper arms and lower legs before and after intervention by means of a standardized quantitative sensory testing battery. ⋯ The PPT can be changed by EA. The PPT increase was confined to the segment of needling, which indicates that it is mainly mediated by segmental inhibition in the spinal cord. This underscores the importance of segmental needling and electrical stimulation in clinical practice.
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In the past, nocebo manipulations have been found to modulate pain perception and influence long-term habituation to pain. Recently, neural correlates accompanying this finding have been identified: habituation over days is mirrored by decreased activity in pain-processing brain areas, whereas nocebo-specific modulation specifically involves the opercular cortex. Focusing on duration and central network characteristics of nocebo information in a longitudinal heat pain paradigm, we investigated 40 healthy participants over a period of 21 consecutive days, whereof sessions on days 1, 8, 14, and 21 were performed during functional magnetic resonance imaging scanning. ⋯ Consistent with previous results, the nocebo manipulation not only modulated pain perception but also was accompanied by the activation of the operculum over an extended period of time. Importantly, the operculum exhibited changes in coupling during nociceptive input over time, as demonstrated by decreased connectivity with the basal ganglia and pinpoints differences, depending on whether a nocebo context was given. These data suggest that negative verbal suggestions prognosticating increasing pain may prevail by modulating basal ganglia-thalamocortical loops.
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Glutamate serves as the primary excitatory neurotransmitter in the nervous system. Previous studies have identified a role for glutamate and group I metabotropic receptors as targets for study in peripheral inflammatory pain. However, the coordination of signaling events that transpire from receptor activation to afferent neuronal sensitization has not been explored. ⋯ In dissociated primary afferent neurons, mGluR5 activation increases TRPV1 responses in an AKAP-dependent manner through a mechanism that induces AKAP association with TRPV1. Experimental results presented herein identify a mechanism of receptor-driven scaffolding association with ion channel targets. Importantly, this mechanism could prove significant in the search for therapeutic targets that repress episodes of acute pain from becoming chronic in nature.
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Editorial Comment
Mechanism-based therapy of neuropathic pain - a concept in danger?
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Randomized Controlled Trial Clinical Trial
Pain relief with lidocaine 5% patch in localized peripheral neuropathic pain in relation to pain phenotype.
In neuropathic pain with irritable nociceptor (IN) phenotype, upregulation of sodium channels on nociceptors is supposed to be an important pain mechanism that may be targeted by topical sodium channel blockade. This randomised, double-blind, phenotype panel, crossover study with 4-week treatment periods of lidocaine 5% patch and placebo was performed to search for phenotype differences in effect. The primary efficacy measure was the total pain intensity on an 11-point numeric rating scale, and the primary objective was to compare the effect of lidocaine in patients with and without IN phenotype as defined by hypersensitivity and preserved small-fibre function determined by quantitative sensory testing. ⋯ For these measures, there was no significant interaction between treatment and phenotype, but there was a significant interaction for pain paroxysms (0.8, 95% CI: 0.4-1.2, P < 0.001) and deep aching pain (0.6, 95% CI: 0.1-1.0, P = 0.013). In conclusion, lidocaine 5% patch had an effect on peripheral neuropathic pain, and it may be most efficacious in patients with IN phenotype. The lack of significant phenotype differences may be caused by too low statistical power.