Articles: hyperalgesia.
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Neuroscience letters · Mar 2002
Effects of electroacupuncture on the mechanical allodynia in the rat model of neuropathic pain.
The analgesic effects of acupuncture on the mechanical allodynia in the rat model of neuropathic pain have not yet been studied. The aim of the present study is: first, to determine if electroacupuncture (EA) or morphine attenuates the mechanical allodynia; and secondly, to examine if the EA effect may be mediated by endogenous opioids. To produce neuropathic pain, the right superior caudal trunk was resected between the S3 and S4 spinal nerves. ⋯ In addition, the antiallodynic effect of Houxi EA was blocked by pretreatment with naloxone (2 mg/kg, i.p.). However, combined application of EA and morphine did not show an obvious synergistic effect. These results suggest that low frequency EA or morphine can relieve the mechanical allodynia signs and the EA effect can be mediated by endogenous opioid systems.
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Randomized Controlled Trial Clinical Trial
Quantitative and qualitative perceptual analysis of cold dysesthesia and hyperalgesia in fibromyalgia.
Somatosensory perception thresholds, perceived intensity, and quality of perceptions were assessed in 20 women with fibromyalgia syndrome (FMS) and in 20 healthy age-matched female controls. All patients and controls scaled perceived intensity and described perceived quality of randomized thermal (Thermotest) and tactile (von Frey filaments) stimulation. Perceived intensity was scaled by free-number magnitude estimation and interindividual comparability was accomplished by Master Scaling. ⋯ The combination of cold hyperesthesia, cold dysesthesia, and multimodal hyperalgesia suggests a selective pathophysiology at a particular level of integration, possibly in the insular cortex. It is suggested that the aberrations revealed by the supraliminal sensory evaluation may be generic for FMS. Particularly, the aberrations established in all patients for perceived quality and intensity in the cold sensory channel may be an additional diagnostic criterion.
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It is still unclear whether the quality of painful thermal sensation is determined only by conduction in specific, dedicated nociceptive channels (i.e. C or Adelta nociceptors) or whether it is a result of integrated activity in both nociceptive and non-nociceptive systems. To evaluate this question, we conducted quantitative and qualitative somatosensory testing in spinal cord injury subjects who suffered from partial or complete loss of thermal sensibility. ⋯ In these areas, both noxious heat and cold elicited a sensation of heat pain. No consistent pattern of heat-elicited pain was observed in areas in which only cold sensation was intact. These data suggest that the integrity of non-noxious thermal systems is essential for the normal perception of thermal pain, and that the subjective sensation of pain depends on the integration of information from nociceptive and non-nociceptive channels.
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After a focal thermal injury to the heel of a rat, thermal hyperalgesia appears at the injury site (primary thermal hyperalgesia), and tactile allodynia appears at the off-injury site (secondary tactile allodynia). The pharmacology of spinal glutamatergic receptors in the initiation and maintenance of secondary tactile allodynia was examined. ⋯ Spinal AMPA-KA receptors play a major role in the initiation of secondary tactile allodynia induced by focal thermal injury. In contrast, spinal NMDA receptors play only a minimal role.
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Cyclooxygenase-2 (COX-2), the inducible isoform of COX, has been identified as the key enzyme to regulate prostaglandin E2 synthesis in inflammatory conditions. Although it has been reported that COX-2 is present in herniated disc samples obtained from patients, little is known concerning the relationships between COX-2 and painful radiculopathy. The purpose of this study was to evaluate whether epidural injection of COX-2 inhibitor abolishes hyperalgesia induced by nucleus pulposus, which is a pain-related behavior in the rat. ⋯ There were no significant differences in sensitivity to thermal noxious stimuli after either application of the nucleus pulposus or epidural injections. These results suggest that prostaglandins and thromboxane, which are produced by COX-2 in inflammatory cells, appear to be related to the inflammatory process produced by application of nucleus pulposus to the nerve root. It is possible that COX-2 plays a significant role in painful radiculopathy following herniated nucleus pulposus.