Articles: hyperalgesia.
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Neonatal pain and inflammation may lead to a long-term effect on nociceptive processing in adults. The current study examined the characteristics of postoperative incisional pain behaviors in adult rats that were subjected to neonatal peripheral inflammation. ⋯ The authors' results suggest that early inflammatory insults during the neonatal period could produce excessive incision-associated mechanical pain hypersensitivity in adult rats. Spinal cord N-methyl-D-aspartate receptors and downstream nitric oxide signaling might contribute to this abnormal pain hypersensitivity, although the mechanisms underlying the long-term effect of neonatal inflammation are still unclear.
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Anesthesia and analgesia · Jun 2007
Randomized Controlled Trial Comparative StudyModulation of remifentanil-induced postinfusion hyperalgesia by propofol.
Experimental and clinical studies suggest that brief opioid exposure can enhance pain sensitivity. During anesthesia, however, opioids are commonly administered in combination with either IV or inhaled hypnotic drugs. In this investigation we sought to determine the analgesic and antihyperalgesic properties of propofol in subhypnotic concentrations on remifentanil-induced postinfusion hypersensitivity in an experimental human pain model. ⋯ The results suggest clinically relevant interactions of propofol and remifentanil in humans, since propofol led to a delay and a weakening of remifentanil-induced postinfusion anti-analgesia in humans. Nevertheless, pronociceptive effects were not completely antagonized by propofol, which may account for the increased demand for analgesics after remifentanil-based anesthesia in clinical practice.
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The aim of this study was to investigate local opioid effects in the inflamed skin of healthy human volunteers. To induce inflammation, the circular tip of a 10-mm-diameter probe was heated to 48 degrees C and applied for 120 seconds to a site on each forearm of 24 healthy participants. Thirty minutes later, 0.2 mL of normal saline was injected subcutaneously into 1 inflamed site, and the opioid antagonist naloxone hydrochloride (80 microg in 0.2 mL) was injected subcutaneously into the other inflamed site. Participants completed tests of pain sensitivity (heat pain thresholds, heat pain ratings, and mechanical pain ratings) before and after the injections. Fentanyl citrate (10 microg in 0.2 mL) was then injected into the pretreated sites, and pain sensitivity was measured again. The thermal injuries produced thermal and mechanical hyperalgesia that did not differ between the saline and naloxone sites. After the fentanyl injections, decreases in thermal and mechanical hyperalgesia were greater at the saline site than the naloxone site. These findings demonstrate that pretreatment with naloxone blocks local opioid effects produced by the subcutaneous injection of a low dose of fentanyl in the inflamed skin of healthy humans. Thus, peripheral opioid receptors could be a therapeutic target for painful cutaneous disorders. ⋯ This article demonstrates that activation of opioid receptors in the skin inhibits sensitivity to painful mechanical and thermal stimuli. Thus, local application of low-dose opioid medications could relieve painful skin disorders.
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Best Pract Res Clin Rheumatol · Jun 2007
ReviewPathophysiological mechanisms in chronic musculoskeletal pain (fibromyalgia): the role of central and peripheral sensitization and pain disinhibition.
Chronic musculoskeletal pain has biological, psychological and social components. This review deals with the biological factors, with emphasis on the fibromyalgia syndrome (FMS). ⋯ Further research is necessary in order to determine which methods are best for diagnosis of the pain hypersensitivity in clinical practice. FMS may be the far end of a continuum that starts with chronic localized/regional musculoskeletal pain and ends with widespread chronic disabling pain.
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Acta Anaesthesiol Taiwan · Jun 2007
Effect of intrathecal NG-nitro-L-arginine methyl ester administration on Fos expression in the spinal dorsal horn in rats following sciatic nerve ligation.
In the available literature, the pro- or antinociceptive role of nitric oxide (NO) is warmly disputed. As a marker of neuronal activation of the central nervous system, Fos expression has been widely used to assess the change in central neuronal activity evoked by peripheral input. In this study, we examined the effect of intrathecal L-NAME, a non-selective nitric oxide synthase (NOS) inhibitor, on nociceptive behavior and spinal Fos expression in rats following chronic constriction injury (CCI) of sciatic nerve, a model of neuropathic pain similar to that observed in clinical setting. ⋯ Spinal Fos expression could be induced by different mechanisms, and it should not regarded as a reliable marker of pain sensation disorders. NO plays an important role in the development of nociception and spinal Fos expression through central sensitization mediated by peripheral nerve injury.