Articles: hyperalgesia.
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Recent studies suggest that calcium contributes to peripheral neural mechanisms of hyperalgesia associated with nerve damage. In this animal behavioural study, we examined further the contribution of calcium in neuropathic pain by testing whether subcutaneous administration of either a calcium chelating agent or voltage-dependent calcium channel blockers attenuate nerve injury-induced hyperalgesia to mechanical stimulation. Studies were carried out in animals with partially ligated sciatic nerves, an established animal model of neuropathic pain. ⋯ In control experiments, SNX-111 had no effect on mechanical thresholds when administered subcutaneously in either the hindpaw of normal animals or the back of the neck in nerve injury animals. This study shows that neuropathic pain involves a local calcium-dependent mechanism in the receptive field of intact neurons of an injured nerve, since it can be alleviated by subcutaneous injections of either a calcium chelating agent or SNX-111, a N-type calcium channel blocker. These agents may be effective, peripherally acting therapeutic agents for neuropathic pain.
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Naunyn Schmiedebergs Arch. Pharmacol. · Aug 1998
Effect of colchicine on nerve growth factor-induced leukocyte accumulation and thermal hyperalgesia in the rat.
In addition to its neuronal effects, nerve growth factor (NGF) is known to act on inflammatory and immune cells. The aim of the present study was to investigate the effect of colchicine on NGF-induced leukocyte accumulation and thermal hyperalgesia. Initial experiments showed that intradermal injection of recombinant human (rh) NGF (0.8 and 4 microg) caused a longlasting increase in tissue myeloperoxidase (MPO) indicating leukotactic activity of NGF. ⋯ In vitro, colchicine (0.4-12 microg/ml) did not significantly influence NGF (10 ng/ml)-induced histamine release from rat peritoneal cells, suggesting that a mast cell stabilizing effect of colchicine did not contribute to inhibition of NGF-induced thermal hyperalgesia. The results show that NGF causes localized indometacin-resistant thermal hyperalgesia that can be blocked by the microtubule disrupting agent colchicine. These results raise the possibility that a mechanism by which NGF produces peripheral sensitization is related to its leukotactic effect.
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Neuroscience letters · Jul 1998
Increased capsaicin-induced secondary hyperalgesia as a marker of abnormal sensory activity in patients with fibromyalgia.
In this study, capsaicin-induced secondary hyperalgesia was assessed as a marker of abnormal nociceptive processing in patients with fibromyalgia (FM). The area of mechanical secondary hyperalgesia induced by a standard solution of capsaicin placed on the volar forearm was measured in ten patients with FM and the results compared to those obtained in ten patients with rheumatoid arthritis (RA) and ten normal subjects. ⋯ In the FM group the area of hyperalgesia correlated with the overall pain score and with the joint tenderness score. The results suggest that in FM there is enhanced sensitivity of nociceptive neurones at a spinal level, thereby supporting the concept of a generalised disturbance of pain modulation in this disorder.
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For years, physical therapists have been utilizing a variety of modalities, including transcutaneous electrical nerve stimulation (TENS), in an attempt to manage pain associated with inflammation. However, the data on clinical effectiveness is conflicting and the neurophysiological mechanism of action is not known. The purpose of this study was to investigate the effects of high and low frequency TENS on the secondary hyperalgesia that occurs after joint inflammation. ⋯ There was no effect of TENS on spontaneous pain behaviors or joint swelling when compared to controls. Thus, TENS appears to be more effective in reducing referred pain (or secondary hyperalgesia) without affecting guarding or splinting of the affected limb. Thus, clinically, the choice to use TENS may depend on patient symptoms; specifically TENS should be effective in reducing referred or radiating pain.
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The veterinary journal · Jul 1998
The influence of lesion type on the duration of hyperalgesia associated with hindlimb lameness in dairy cattle.
The nociceptive thresholds of 42 sound dairy cattle were compared with 53 animals displaying hind-claw lameness. All animals in the study were lameness scored and nociceptive threshold tested. Each animal then received a routine claw trim while the lame cattle also had the cause of lameness determined and treated. ⋯ The group which were retested on day 28 were subdivided by lesion type: sole ulcer; white line disease and acute digital tissue infection. Each lesion type caused a decreased nociceptive threshold at day 1. At re-evaluation on day 28 only the thresholds of the acute digital tissue infection group were not significantly different from the sound group but thresholds in sole ulcer and white line disease cows were still depressed.