Pain
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The proportion of people 65 years of age and older who report musculoskeletal pain and physical disability is high. The main objective of this study was to determine whether physical disability was associated with the presence of musculoskeletal pain in a sample of senior citizens. Self-administered questionnaires were sent to a sample of 1306 community-dwelling senior citizens in London, Ontario, Canada between August and October 1995. ⋯ Logistic regression analysis, without controlling for potential confounding variables, revealed that those who reported having musculoskeletal pain were seven times more likely to have some difficulty performing three or more activities listed in the questionnaire (OR = 6.91 95% CI 4.92-9.69). When significant confounding variables were controlled in the analysis, seniors who reported musculoskeletal pain were still three times more likely to have some difficulty with three or more activities (OR = 2.93, 95% CI 1.96-4.38). Although no causal relationship can be inferred, thorough pain assessment and pain management may be important in the maintenance of independent living for adults 65 years of age or older.
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Two classes of neurons with distinct responses to opioids have been identified in the rostral ventromedial medulla (RVM), a region with a well-documented role in nociceptive modulation. 'On-cells' are directly inhibited by opioids, and opioids can thus gain access to the modulatory circuitry of the RVM by an action on these neurons. 'Off-cells' are likely to exert a net inhibitory effect on nociceptive processing, and are activated by opioids. Because the opioid activation of off-cells is indirect, it has been proposed that on-cells function as inhibitory interneurons, and that opioid-induced suppression of on-cell firing in turn activates off-cells via disinhibition. The aim of the present study was to test this possibility. ⋯ These results demonstrate that a burst of on-cell firing is not required in order for the off-cell to exhibit a reflex-related pause in discharge, and do not support the proposed crucial role for on-cells as inhibitory interneurons within the RVM. In addition, preferential suppression of on-cell tiring was not associated with an increase in tail flick latency. This suggests that, under the conditions of these experiments, on-cell discharge is not a potent regulator of moment-to-moment variations in nociceptive responsiveness.
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Intraspinal injections of the AMPA-metabotropic receptor agonist quisqualic acid (QUIS) were made in an effort to simulate injury induced elevations of excitatory amino acids (EAAs), a well documented neurochemical change following spinal cord injury (SCI). The progressive pathological sequela associated with QUIS injections closely resembles the cascade of events described following ischemic and traumatic SCI and the pathogenesis of cavities in the clinical condition of post-traumatic syringomyelia. ⋯ Thus, the present results provide a morphological correlate of spontaneous and evoked pain related behaviors following excitotoxic SCI. The behavioral characteristics combined with the similarities between QUIS induced injury and the clinical pathology of SCI support the use of the excitotoxic model in studies related to the central mechanism(s) of altered sensation, including pain, following spinal injury.
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The psychological assessment of chronic pain is often accomplished using questionnaires such as the (West Haven-Yale) Multidimensional Pain Inventory ((WHY)MPI) which is constructed to capture the multidimensionality of chronic pain. The (WHY)MPI theoretically originates from behavioural and cognitive behavioural theories of pain. It is divided into three parts and measures psychosocial and behavioural consequences of pain. ⋯ This part of the inventory is designed to measure the extent of different types of activities, and our results suggest that this section may only be used for assessing general activity level. We conclude that, with a few adjustments, the analyses yielded satisfactory results for sections 1 and 2 of the MPI-S regarding its factor structure, reliability and generalisability. For section 3 the hypothesised factor structure could not be confirmed.
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Nociceptive electrical stimuli were applied to the sural nerve during hypnotically-suggested analgesia in the left lower limb of 18 highly susceptible subjects. During this procedure, the verbally reported pain threshold, the nociceptive flexion (RIII) reflex and late somatosensory evoked potentials were investigated in parallel with autonomic responses and the spontaneous electroencephalogram (EEG). The hypnotic suggestion of analgesia induced a significant increase in pain threshold in all the selected subjects. ⋯ No modification in the autonomic parameters or the EEG was observed. These data suggest that different strategies of modulation can be operative during effective hypnotic analgesia and that these are subject-dependent. Although all subjects may shift their attention away from the painful stimulus (which could explain the decrease of the late somatosensory evoked potentials), some of them inhibit their motor reaction to the stimulus at the spinal level, while in others, in contrast, this reaction is facilitated.