Pain
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Approximately 7% to 10% of patients develop a chronic pain syndrome after stroke. This chronic pain condition is called central poststroke pain (CPSP). Recent studies have observed an abnormal increase in the secretion of brain-derived neurotrophic factor (BDNF) in spinal cord tissue after spinal cord injury. ⋯ Instead of being inhibited by the γ-aminobutyric acid (GABA) system in normal rats, multiunit activity in the MT was enhanced after a microinjection of muscimol, a GABAA receptor agonist, in CPSP animals. After CPSP, BDNF expression was enhanced in the MT, whereas the expression of GABAA channels and the cotransporter KCC2 decreased in the same area. These findings suggest that neuronal plasticity in the MT that was induced by BDNF overexpression after the thalamic lesion was a key factor in CPSP.
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Changes in chloride reversal potential in rat spinal cord neurons have previously been associated with persistent pain in nerve injury and inflammation models. These changes correlate with a decrease in the expression of the potassium chloride transporter, KCC2, and with increases in neuronal excitability. Here, we test the hypothesis that similar changes occur in mice with neuropathic pain induced by chronic constriction injury of the trigeminal infraorbital nerve (CCI-ION). ⋯ Quantitative real-time polymerase chain reaction analysis revealed no significant changes, at either 3 to 5 days or 12 to 14 days after CCI-ION, in either KCC2 or NKCC1. These findings suggest that CCI-ION in mice results in transient and modest changes in chloride reversal potentials, and that these changes may not persist during the late phase. This suggests that, in the mouse model of CCI-ION, chloride dysregulation may not have a prominent role in the central mechanisms leading to the maintenance of chronic pain.
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The aim of this study was to evaluate the incidence and clinical features of musculoskeletal pain (MSP) in patients with Parkinson disease (PD) compared with a control group without the disease. The retrospective cohort study used a subset of the Taiwan National Health Insurance Research Database (NHIRD) comprising information on 1 million beneficiaries randomly sampled from the entire population of Taiwan. A total of 490 patients aged 50 and above with newly diagnosed Parkinson disease were identified during a period from 2000 to 2005. ⋯ This study showed that the PD may significantly increase the risk of developing MSP. The risk of developing MSP seems to be greatest for middle-aged male patients with PD. Clinicians should be more alert for MSP in patients with PD, and early intervention should be considered.
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Randomized Controlled Trial
Midazolam as an active placebo in three fentanyl-validated nociceptive pain models.
The use of inactive placebos in early translational trials of potentially analgesic compounds is discouraged because of the side-effect profiles of centrally acting analgesics. Therefore, benzodiazepines are used, although their use has not been validated in this context. Whether benzodiazepines confound the results of acute pain tests is unknown. ⋯ The findings of this study show that midazolam can be used as an active placebo in analgesic drug trials. Furthermore, the proposed models were simple to implement and very effective in detecting analgesia. The test battery can be used in translational trials for new compounds and comes with an active placebo and an optional active comparator.
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Previous research suggests that for people living with chronic pain, pain expectancy can undermine access to adaptive resources and functioning. We tested and replicated the unique effect of pain expectancy on subsequent pain through 2 daily diary studies. We also extended previous findings by examining cognitive and affective antecedents of pain expectancy and the consequences of pain expectancy for daily social enjoyment and stress. ⋯ Consistent with study 1, more than usual evening pain expectancy was related to greater next morning pain. We also found that next morning pain predicted next afternoon social enjoyment but not social stress. The findings of these 2 studies point to the importance of promoting positive affect and reducing pain expectancy as a way of decreasing the detrimental effect of chronic pain on enjoyable social experiences.