Pain
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We previously developed a model of opioid-induced neuroplasticity in the peripheral terminal of the nociceptor that could contribute to opioid-induced hyperalgesia, type II hyperalgesic priming. Repeated administration of mu-opioid receptor (MOR) agonists, such as DAMGO, at the peripheral terminal of the nociceptor, induces long-lasting plasticity expressed, prototypically as opioid-induced hyperalgesia and prolongation of prostaglandin E2-induced hyperalgesia. In this study, we evaluated the mechanisms involved in the maintenance of type II priming. ⋯ A second model of priming, latent sensitization, induced by complete Freund's adjuvant was also reversed, in males. In females, the inhibitor combination was only able to inhibit the expression and maintenance of DAMGO-induced priming when knockdown of G-protein-coupled estrogen receptor 30 (GPR30) in the nociceptor was performed. These findings demonstrate that the maintenance of DAMGO-induced type II priming, and latent sensitization is mediated by an interaction between, Src and MAP kinases, which in females is GPR30 dependent.
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[This corrects the article DOI: 10.1097/j.pain.0000000000000733.].
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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.