Pain
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Comparative Study
Inflammation-induced decrease in voluntary wheel running in mice: a nonreflexive test for evaluating inflammatory pain and analgesia.
Inflammatory pain impacts adversely on the quality of life of patients, often resulting in motor disabilities. Therefore, we studied the effect of peripheral inflammation induced by intraplantar administration of complete Freund's adjuvant (CFA) in mice on a particular form of voluntary locomotion, wheel running, as an index of mobility impairment produced by pain. The distance traveled over 1 hour of free access to activity wheels decreased significantly in response to hind paw inflammation, peaking 24 hours after CFA administration. ⋯ The CFA-induced decrease in voluntary wheel running was dose-dependently reversed by subcutaneous administration of antiinflammatory and analgesic drugs, including naproxen (10-80 mg/kg), ibuprofen (2.5-20mg/kg), diclofenac (1.25-10mg/kg), celecoxib (2.5-20mg/kg), prednisolone (0.62-5mg/kg), and morphine (0.06-0.5mg/kg), all at much lower doses than reported in most rodent models. Furthermore, the doses that induced recovery in voluntary wheel running did not reduce CFA-induced mechanical allodynia, indicating a greater sensitivity of the former as a surrogate measure of inflammatory pain. We conclude that monitoring changes in voluntary wheel running in mice during peripheral inflammation is a simple, observer-independent objective measure of functional changes produced by inflammation, likely more aligned to the global level of pain than reflexive measures, and much more sensitive to analgesic drug effects.
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Comparative Study
A critical period in the supraspinal control of pain: opioid-dependent changes in brainstem rostroventral medulla function in preadolescence.
We have previously shown that the balance of electrically evoked descending brainstem control of spinal nociceptive reflexes undergoes a switch from excitation to inhibition in preadolescent rats. Here we show that the same developmental switch occurs when μ-opioid receptor agonists are microinjected into the rostroventral medulla (RVM). Microinjections of the μ-opioid receptor agonist [D-Ala(2), N-MePhe(4), Gly-ol]-enkephalin (DAMGO) into the RVM of lightly anaesthetised adult rats produced a dose-dependent decrease in mechanical nociceptive hindlimb reflex electromyographic activity. ⋯ Enhancing opioidergic activity with chronic morphine over P7 to P14 accelerated this development. These results show that descending facilitation of spinal nociception in young animals is mediated by μ-opioid receptor pathways in the RVM. Furthermore, the developmental transition from RVM descending facilitation to inhibition of pain is determined by activity in central opioid networks at a critical period of periadolescence.
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Randomized Controlled Trial Comparative Study
Patients who display protective pain behaviors are viewed as less likable, less dependable, and less likely to return to work.
In the present study, participants (ie, observers) watched video sequences of patients with chronic back pain performing a physically demanding lifting task. Participants were asked to make judgments about patients' levels of pain and readiness to work. For each patient, observers were also asked to make judgments about personality traits relevant to work performance and employment. ⋯ Analyses also revealed that patients displaying protective pain behaviors were perceived as being significantly less likable, less dependable, and less ready to work than patients displaying other forms of pain behavior. Discussion addresses the processes by which pain behaviors might influence observers' judgments about patients' personality traits and readiness to work. Implications of the present findings for clinical practice and the management of patients presenting with pain conditions are also discussed.
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Randomized Controlled Trial Comparative Study
Effects of strength vs aerobic exercise on pain severity in adults with fibromyalgia: a randomized equivalence trial.
Strength training and aerobic exercise have beneficial effects on pain in adults with fibromyalgia. However, the equivalence of strengthening and aerobic exercise has not been reported. The primary aim of this randomized equivalence trial involving patients with fibromyalgia admitted to an interdisciplinary pain treatment program was to test the hypothesis that strengthening (n=36) and aerobic (n=36) exercise have equivalent effects (95% confidence interval within an equivalence margin ± 8) on pain, as measured by the pain severity subscale of the Multidimensional Pain Inventory. ⋯ Significant improvements in pain severity (P<.001), peak Vo(2) (P<.001), strength (P<.001), and pain thresholds (P<.001) were observed from baseline to week 3 in the intent-to-treat analysis; however, patients in the aerobic group (mean change 2.0 ± 2.6 mL/kg/min) experienced greater gains (P<.013) in peak Vo(2) compared to the strength group (mean change 0.4 ± 2.6 mL/kg/min). Knowledge of the equivalence and physiological effects of exercise have important clinical implications that could allow practitioners to target exercise recommendations on the basis of comorbid medical conditions or patient preference for a particular type of exercise. This study found that strength and aerobic exercise had equivalent effects on reducing pain severity among patients with fibromyalgia.
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Comparative Study
Effects of acute postoperative pain on catecholamine plasma levels, hemodynamic parameters, and cardiac autonomic control.
Postoperative pain is often stated to be a significant contributor to a sympathetic stress response after surgery. However, hardly any evidence has been published to support this assumption. Hence it was the aim of this trial to investigate the relationship between postoperative pain and hemodynamic, endocrine, and autonomic parameters. ⋯ This was also found for MAP, but not for EPI or the parameters of HRV, HR, and RR. In contrast to common belief, the severity of postoperative pain does not appear to be associated with the degree of sympathetic stress response after surgery, and other factors such as surgical trauma may be more important. Importantly, the absence of signs of sympathetic stimulation cannot be seen as a guarantee for the absence of significant pain.