European journal of pain : EJP
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We have recently shown that visual deprivation from birth exacerbates responses to painful thermal stimuli. However, the mechanisms underlying pain hypersensitivity in congenital blindness are unclear. ⋯ The increased sensitivity to painful thermal stimulation in congenital blindness may be due to more efficient central processing of C-fibre-mediated input, which may help to avoid impending dangerous encounters with stimuli that threaten the bodily integrity. WHAT DOES THIS STUDY ADD?: Hypersensitivity to heat pain in congenital blindness is associated with faster responses to C-fibre activation, likely caused by more efficient central processing of C-fibre-mediated input.
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Observational Study
Perceived pain extent is associated with disability, depression and self-efficacy in individuals with whiplash-associated disorders.
Completion of a pain drawing is a familiar task in those presenting with whiplash-associated disorders (WAD). Some people report pain almost over their entire body. Yet the reasons for larger pain extent have not been fully explored. ⋯ By utilizing a novel method for pain extent quantification, this study shows that widespread pain is associated with a number of factors including perceived disability, depression and self-efficacy in individuals with chronic WAD. Widespread pain should alert the clinician to consider more specific psychological screening, particularly for depression and self-efficacy, in patients with WAD. WHAT DOES THIS STUDY ADD?: Women with chronic WAD, those with unsettled insurance claims and those with poorer financial status perceive more widespread pain. When controlling for these factors, larger pain areas remain associated with perceived pain and disability, depression and self-efficacy. The pain drawing is useful to support psychological screening in people with chronic WAD.
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Stressful experiences can produce analgesia, termed stress-induced analgesia (SIA). Meanwhile, it has been widely established that the mesolimbic dopamine pathway and nucleus accumbens (NAc) have a profound role in pain modulation. In this study, we examined the role of accumbal dopamine receptors in antinociception caused by forced swim stress (FSS) in order to understand more about the function of these receptors within the NAc in FSS-induced analgesia. ⋯ Forced swim stress (FSS) induces the antinociception in both phases of formalin test. Blockade of accumbal dopamine receptors attenuate the antinociception induced by FSS. Stress-induced analgesia is dose-dependently reduced by dopamine receptor antagonists in both phases, although it is more prominent during the late phase.
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Preclinical drug discovery for the treatment of chronic pain is at present challenged by the difficulty to study behaviours comparable to the complex human pain experience in animals. Several reports have demonstrated a frequent association of chronic pain in humans with affective disorders, such as anxiety and depression, and impaired cognitive functions, including memory and decision making, and motivation for goal-directed behaviours. In this study, we validated different behavioural outcomes to measure the emotional and cognitive manifestations of neuropathic pain induced in mice by partial sciatic nerve ligation. ⋯ These results indicate that some emotional manifestations of chronic pain do not necessarily resolve when pain is relieved and underline the relevance to evaluate multiple behavioural responses associated with chronic pain, including the affective-motivational and cognitive behaviours, to increase the predictive value of preclinical drug discovery. WHAT DOES THIS STUDY ADD?: In this study, we have validated different behavioural outcomes allowing a reliable measurement of the emotional and cognitive manifestations of neuropathic pain induced in mice by partial sciatic nerve ligation. These results underline the relevance to evaluate these multiple pain-related alterations to improve the predictive value of preclinical drug discovery.
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Randomized Controlled Trial
A randomized phase I trial evaluating the effects of inhaled 50-50% N2 O-O2 on remifentanil-induced hyperalgesia and allodynia in human volunteers.
Opioids are known to relieve pain, and also aggravate pre-existing hyperalgesia. In animal studies, the N-methyl-d-aspartate-receptor antagonist nitrous oxide (N2 O) was able to prevent hyperalgesia. The present study evaluated the effect of N2 O on hyperalgesia after remifentanil infusion in healthy volunteers. ⋯ Nitrous oxide significantly reduced hyperalgesia, allodynia and pain intensity aggravated after remifentanil administration in a human volunteer model. WHAT DOES THIS STUDY ADD?: This study brings the evidence that N2 O reduces the remifentanil aggravated secondary hyperalgesia in human volunteers exposed to a well-known model of electrical pain. N2 O was able to oppose the hyperalgesia, the allodynia and the pain intensity consecutive to remifentanil use in this specific pain model.