Pain
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"Don't look and it won't hurt" is commonly heard advice when receiving an injection, which implies that observing needle pricks enhances pain perception. Throughout our lives, we repeatedly learn that sharp objects cause pain when penetrating our skin, but situational expectations, like information given by the clinician prior to an injection, may also influence how viewing needle pricks affects forthcoming pain. How both previous experiences and acute situational expectations related to viewing needle pricks modulate pain perception is unknown. ⋯ Intensity ratings of electrical stimuli were higher when a clip was associated with expectation of painful compared to nonpainful stimuli, suggesting that situational expectations about forthcoming pain bias perceived intensity. Unpleasantness ratings and pupil dilation responses were higher when participants viewed a needle prick, compared to when they viewed a Q-tip touch, suggesting that previous experiences with viewing needle pricks primarily act upon perceived unpleasantness. Thus, remote painful experiences with viewing needle pricks, together with information given prior to an injection, differentially shape the impact of viewing a needle prick on pain perception.
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N-Methyl-d-aspartate (NMDA) receptors are thought to play an important role in the processes of central sensitization and pathogenesis of neuropathic pain, particularly after spinal cord injury (SCI). NMDA antagonists effectively reduce neuropathic pain, but serious side effects prevent their use as therapeutic drugs. NMDA NR2B antagonists have been reported to effectively reduce inflammatory and neuropathic pain. ⋯ Increased expression of NR2B in the hemisection model was reduced by intrathecal ifenprodil. These results suggest that intrathecal NMDA NR2B antagonist increased the mechanical nociceptive threshold after SCI without motor depression. A selective subtype of NMDA receptor, such as NR2B, may be a more selective target for pain control because NMDA receptors play a crucial role in the development and maintenance of chronic pain.
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The effects of deep brain stimulation of the subthalamic nucleus on nonmotor symptoms of Parkinson's disease (PD) rarely have been investigated. Among these, sensory disturbances, including chronic pain (CP), are frequent in these patients. The aim of this study was to evaluate the changes induced by deep brain stimulation in the perception of sensory stimuli, either noxious or innocuous, mediated by small or large nerve fibers. ⋯ Pain provoked by thermal stimuli was reduced when the stimulator was turned on. Motor improvement positively correlated with changes in warm detection and heat pain thresholds. Subthalamic nucleus deep brain stimulation contributes to relieve pain associated with PD and specifically modulates small fiber-mediated sensations.
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Locomotor disability (LMD) is common at older ages, and can lead to other significant disability and mortality. Prevalent pain has been shown to be associated with LMD. This article aimed to assess the association between changes in lower limb pain status (ascertained from a manikin) and changes in the level of self-reported LMD in a sample of UK adults age ≥ 50years, over a 6-year period (data collected at 3-year intervals). ⋯ Becoming free from lower limb pain was associated with a relative decrease in LMD, but did not return LMD scores to the level of those who had remained pain-free throughout. This is consistent with a cumulative effect on LMD of recurrent episodes of pain. Lower limb pain may be a key target for prevention and rehabilitation to reduce years lived with disability in later life.