Pain
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Although the administration of opioids is the most effective treatment for pain, their efficacy is limited by the development of tolerance. The midbrain periaqueductal gray matter (PAG) participates in opioid analgesia and tolerance. Microinjection of morphine into PAG produces antinociception, probably through neurons in the rostral ventromedial medulla (RVM), namely through the activation of off-cells, which inhibit nociception, and the inhibition of on-cells, which facilitate nociception. ⋯ In contrast to saline-pretreated rats, PAG microinjection of morphine in tolerant animals did not change the baseline activity of off- or on-cells, did not prevent the off-cell pause or the on-cell activation upon tail heating, and did not lengthen the tail flick latency. However, microinjection of kainic acid into the PAG (1) caused off-cells to become continuously active and on-cells to become silent, and (2) prevented the tail flick, i.e. exactly what morphine did before tolerance developed. These results demonstrate a correspondence between neuronal and behavioral measures of tolerance to PAG opioid administration, and suggest that tolerance is mediated by a change in opioid-sensitive neurons within the PAG.
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This study reports chronic pain prevalence in a randomly selected sample of the adult Australian population. Data were collected by Computer-Assisted Telephone Interview (CATI) using randomly generated telephone numbers and a two-stage stratified sample design. Chronic pain was defined as pain experienced every day for three months in the six months prior to interview. ⋯ Within the subgroup of respondents reporting chronic pain, the presence of interference with daily activities caused by pain was significantly associated with younger age; female gender; and not having private health insurance. There were strong associations between having interfering chronic pain and receiving disability benefits (adjusted OR=3.31, P<0.001) or being unemployed due to health reasons (adjusted OR=7.94, P<0.001, respectively). The results show that chronic pain impacts upon a large proportion of the adult Australian population, including the working age population, and is strongly associated with markers of social disadvantage.
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A growing body of evidence supports a nicotinic cholinergic approach to pain management, as neuronal nicotinic receptor agonists have shown efficacy across animal models of both inflammatory and neuropathic pain. However, most of these investigations have focused on the spinal system, and there is to date no report of nicotinic receptor-mediated antinociception in any pain model involving the trigeminal field of innervation. Thus, the purpose of the present studies was to evaluate whether the neuronal nicotinic receptor agonist epibatidine possesses antihyperalgesic activity in the formalin model of facial pain. ⋯ Finally, pretreatment with the selective neuronal nicotinic receptor antagonist mecamylamine completely abolished the antihyperalgesic effect of epibatidine in both phases. Taken together, these studies demonstrate that in both the acute and tonic phases of the formalin model of facial pain, epibatidine produces a neuronal nicotinic receptor-mediated antihyperalgesia that is both dose- and time-dependent. These results support the rationale for exploring the clinical efficacy of nicotinic agonists as analgesics to treat certain types of trigeminal pain in humans.
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Randomized Controlled Trial Clinical Trial
A blind, randomized, controlled trial of cognitive-behavioural intervention for patients with recent onset rheumatoid arthritis: preventing psychological and physical morbidity.
This study examined the efficacy of a cognitive and behavioural intervention (CBT) for patients with recent onset, seropositive rheumatoid arthritis. Fifty-three participants with a diagnosis of classical or definite rheumatoid arthritis, who were seropositive and had less than 2 years of disease history were recruited into the trial. All participants received routine medical management during the study, although half were randomly allocated to receive an adjunctive psychological intervention. ⋯ At outcome but not follow-up, the CBT group also showed reduction in C-reactive protein levels. However, the CBT group did show significant improvement in joint involvement at 6-month follow-up compared with the Standard group, indicating physical improvements above those achieved with standard care. These results indicate that cognitive-behavioural intervention offered as an adjunct to standard clinical management early in the course of RA is efficacious in producing reductions in both psychological and physical morbidity