Pain
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The "gate control theory of pain" of 1965 became famous for integrating clinical observations and the understanding of spinal dorsal horn circuitry at that time into a testable model. Although it became rapidly clear that spinal circuitry is much more complex than that proposed by Melzack and Wall, their prediction of the clinical efficacy of transcutaneous electrical nerve stimulation and spinal cord stimulation has left an important clinical legacy also 50 years later. In the meantime, it has been recognized that the sensitivity of the nociceptive system can be decreased or increased and that this "gain control" can occur at peripheral, spinal, and supraspinal levels. ⋯ This hypothesis generation in the diagnostic process is an essential step towards a mechanism-based treatment of pain. The challenge now is to generate the rational basis of multimodal pain therapy algorithms by including profile-based stratification of patients into studies on efficacy of pharmacological and nonpharmacological treatment modalities. This review outlines the current evidence base for this approach.
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Physical activity has multiple health benefits but may also increase the risk of developing musculoskeletal pain (MSP). However, the relationship between physical activity and MSP has not been well characterized. This study examined the dose-response relationship between sports activity and MSP among adolescents. ⋯ In longitudinal analysis, the risk ratio for developing pain at 1-year follow-up per 1 h/wk increase in baseline sports activity was 1.03 (95% confidence interval = 1.02-1.05). Spline models indicated a linear association (P < 0.001) but not a nonlinear association (P ≥ 0.45). The more the adolescents played sports, the more likely they were to have and develop pain.
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We reported earlier that TNF-α, a proinflammatory cytokine implicated in many inflammatory disorders causing orofacial pain, increases the activity of Cdk5, a key kinase involved in brain development and function and recently found to be involved in pain signaling. To investigate a potential mechanism underlying inflammatory pain in trigeminal ganglia (TGs), we engineered a transgenic mouse model (TNF) that can conditionally overexpresses TNF-α upon genomic recombination by Cre recombinase. TNF mice were bred with Nav1.8-Cre mouse line that expresses the Cre recombinase in sensory neurons to obtain TNF-α:Nav1.8-Cre (TNF-α cTg) mice. ⋯ Remarkably, this effect was prevented by roscovitine, an inhibitor of Cdk5, which suggests that TNF-α overexpression induced sensitization of the TRPV1 channel. Furthermore, TNF-α cTg mice displayed more aversive behavior to noxious thermal stimulation (45°C) of the face in an operant pain assessment device as compared with control mice. In summary, TNF-α overexpression in the sensory neurons of TNF-α cTg mice results in inflammatory sensitization and increased Cdk5 activity; therefore, this mouse model would be valuable for investigating the mechanism of TNF-α involved in orofacial pain.
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The introduction of extended-release opioid analgesics helped initiate an epidemic of prescription opioid abuse in the United States. To make access to the drug by crushing or dissolution more difficult, abuse-deterrent formulations (ADFs) of OxyContin (Purdue Pharma, Stamford, CT) and Opana ER (Endo Pharmaceuticals Inc., Malvern, PA), which use the same foundation technology (Intac, Grunenthal, Aachen, Germany), were introduced in 2010 and 2012, respectively. To examine their relative effectiveness, we used a structured survey of 12,124 individuals entering treatment for opioid use disorder followed by a more focused online survey with a subset of these patients (N = 129) using both structured and open-ended questions. ⋯ However, although the Opana ER ADF was effective in reducing insufflation (80%-37.1%), injection (60.0%-51.4%), and overall nonoral abuse (94.3%-77.1%), it showed no significant decrease over time. Bearing in mind that the Opana ER sample was smaller in size than that for OxyContin, our results nonetheless suggest disparate outcomes resulting from the introduction of the ADFs, which could indicate that an ADF's effectiveness may be drug-specific. Given the public health impact of prescription opioids and the considerable effort being expended to develop ADFs as a partial solution to the problem, our preliminary studies suggest that each ADF must be evaluated on its own merits even if the same proprietary technology is used.
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Randomized Controlled Trial
Problem Solving Skills Training for Parents of Children with Chronic Pain: A Pilot Randomized Controlled Trial.
This pilot randomized controlled trial aimed to determine the feasibility, acceptability, and preliminary efficacy of parental problem-solving skills training (PSST) compared with treatment as usual on improving parental mental health symptoms, physical health and well-being, and parenting behaviors. Effects of parent PSST on child outcomes (pain, emotional, and physical functioning) were also examined. Participants included 61 parents of children aged 10 to 17 years with chronic pain randomized to PSST (n = 31) or treatment as usual (n = 30) groups. ⋯ Findings demonstrate that PSST is feasible and acceptable to parents of youths with chronic pain. Treatment outcome analyses show promising but mixed patterns of effects of PSST on parent and child mental health outcomes. Further rigorous trials of PSST are needed to extend these pilot results.