Pain
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Randomized Controlled Trial
Endogenous opioids mediate left dorsolateral prefrontal cortex rTMS-induced analgesia.
The concurrent rise of undertreated pain and opiate abuse poses a unique challenge to physicians and researchers alike. A focal, noninvasive form of brain stimulation called repetitive transcranial magnetic stimulation (rTMS) has been shown to produce acute and chronic analgesic effects when applied to dorsolateral prefrontal cortex (DLPFC), but the anatomical and pharmacological mechanisms by which prefrontal rTMS induces analgesia remain unclear. Data suggest that DLPFC mediates top-down analgesia via gain modulation of the supraspinal opioidergic circuit. ⋯ Naloxone pretreatment significantly reduced the analgesic effects of real rTMS. These results demonstrate that left DLPFC rTMS-induced analgesia requires opioid activity and suggest that rTMS drives endogenous opioidergic pain relief in the human brain. Further studies with chronic dosing regimens of drugs that block or augment the actions of opiates are needed to determine whether TMS can augment opiates in chronic or postoperative pain management.
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Randomized Controlled Trial Comparative Study
Placebo manipulations reduce hyperalgesia in neuropathic pain.
Several studies have shown that placebo analgesia effects can be obtained in healthy volunteers, as well as patients suffering from acute postoperative pain and chronic pain conditions such as irritable bowel syndrome. However, it is unknown whether placebo analgesia effects can be elicited in chronic pain conditions with a known pathophysiology such as a nerve injury. Nineteen patients who had developed neuropathic pain after thoracotomy were exposed to a placebo manipulation in which they received either open or hidden administrations of lidocaine. ⋯ No placebo effect was observed in relation to spontaneous pain or evoked pain, which is most likely due to low pain levels resulting in floor effects. This is the first study to demonstrate a placebo effect in neuropathic pain. The possible mechanisms underlying the placebo effects in hyperalgesia are discussed, and implications for treatment are outlined.
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Chronic low back pain (LBP) is a complex, multifactorial disorder with unclear underlying mechanisms. In humans and rodents, decreased expression of secreted protein acidic rich in cysteine (SPARC) is associated with intervertebral disc (IVD) degeneration and signs of LBP. The current study investigates the hypothesis that IVD degeneration is a risk factor for chronic LBP. ⋯ Morphine (6 mg/kg, i.p.) reduced cutaneous sensitivity and alleviated axial discomfort in SPARC-null mice. Ageing SPARC-null mice mirror many aspects of the complex and challenging nature of LBP in humans and incorporate both anatomic and functional components of the disease. The current study supports the hypothesis that IVD degeneration is a risk factor for chronic LBP.
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Review Meta Analysis Comparative Study
Pain perception in athletes compared to normally active controls: a systematic review with meta-analysis.
This study systematically reviewed differences in pain perception between athletes and normally active controls. We screened MEDLINE, Sport-Discus, EMBASE, Web of Science, PsycINFO, PSYNDEX, and the citations of original studies and systematic reviews. All studies on experimentally induced pain that compared pain perception between athletes and normally active controls were eligible. ⋯ After exclusion of studies with high risk of bias, differences between groups in pain threshold were not significant any longer. Our data suggest that regular physical activity is associated with specific alterations in pain perception. Psychological and biological factors that may be responsible for these alterations are discussed.