Articles: neuralgia.
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Experimental neurology · Aug 1998
Comparative StudyDifferences in sympathetic innervation of mouse DRG following proximal or distal nerve lesions.
Nerve injury leads to novel sympathetic innervation of the dorsal root ganglion (DRG). We have hypothesized previously that the degenerating nerve increases the sympathetic sprouting in the DRG and pain after chronic sciatic constriction injury (CCI) by virtue of its influence on sensory and sympathetic axons spared by the injury. However, L5 spinal nerve ligation and transection (SNL) results in the complete isolation of the L5 DRG from the degenerating stump, yet sympathetic axons invade the ganglion, and sympathetically dependent pain develops. ⋯ Observation of the origins of the invading sympathetic axons revealed that after CCI, sympathetics innervating blood vessels and dura (probably intact) sprouted into the ganglion, but after SNL sympathetics (probably axotomized) invaded from the injured spinal nerve. Based on these findings, we hypothesize that there are two mechanisms for sympathetic sprouting into DRG, differentially dependent on Wallerian degeneration. Analysis of pain behavior in these animals reveals that (i) mechanoallodynia and sympathetic innervation of the DRG tend to coincide and (ii) thermal allodynia and Wallerian degeneration, but not sympathetic innervation of the DRG tend to coincide.
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Sodium channel antagonists have been used in the management of neuropathic pain for several years. Recent evidence suggests that lamotrigine, which is active at glutaminergic excitatory synapses, is very effective in producing pain relief. ⋯ Our results suggest that this novel channel antagonist can be used to treat neuropathic pain. Double blind placebo control studies are therefore needed to substantiate these findings.
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The current study aimed to assess whether local administration of morphine could block the development of hyperalgesia and allodynia in a rat model of osteotomy or bone damage. ⋯ This study shows that local application of a low dose of morphine effectively blocks the development of hyperalgesia and allodynia in a rat model of bone damage through mu-opioid receptor action. These findings provide further evidence that local application of morphine at the time of orthopedic surgery, bone graft, or bone marrow harvesting may reduce the amount of postoperative pain.
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Clinical Trial
[Lidocaine tape (Penles--a dressing tape based on 60% lidocaine--) reduces the pain of postherpetic neuralgia].
The treatment of postherpetic neuralgia (PHN) by topical administration of local anesthetics has a number of drawbacks. Lidocaine tape (Penles) is a 15 cm2 dressing tape based on 60% lidocaine used to anesthetize skin when an intravenous catheter is inserted. This study aims to evaluate the analgesic efficacy of lidocaine tape in patients with PHN by comparing the results with those of surgical drape (Tegaderm). ⋯ Pain score was reduced at measurements taken starting from 1 hour after lidocaine tape application (P < 0.05). Lidocaine tape induced minor side-effects, erythema in a patient and increase in pain in another patient. In conclusion, lidocaine tape is effective for relief of PHN.
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Neuropathic pain accompanies peripheral nerve injury following a variety of insults including metabolic disorders, traumatic injury, and exposure to neurotoxins such as vincristine and taxol. Vincristine, a microtubule depolymerizing drug, produces a peripheral neuropathy in humans that is accompanied by painful paresthesias and dysesthesias (Sandler et al., [1969] Neurology 19:367-374; Holland et al. [1973] Cancer Res. 33:1258-1264). The recent development of an animal model of vincristine-induced neuropathy provides an opportunity to investigate mechanisms underlying this form of neuropathic pain. ⋯ This decrease in microtubule density was due to a significant increase in the cross-sectional area of unmyelinated axons, suggesting swelling of axons. In addition, vincristine-treated axons had significantly fewer microtubules cut in cross-section and significantly more tangentially oriented microtubules per axon compared to controls. These results suggest that vincristine causes disorganization of the axonal microtubule cytoskeleton, as well as an increase in the caliber of unmyelinated sensory axons.