Articles: hyperalgesia.
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Zhonghua yi xue za zhi · Feb 2012
[Changes of glycogen synthase kinase-3β and its phosphorylation in spinal cord neurons in rats with incisional pain-remifentanil-induced hyperalgesia].
To investigate the change in glycogen synthase kinase-3β (GSK-3β) in spinal cord neurons in rats with incisional pain (IP)-remifentanil-induced hyperalgesia. ⋯ These data indicate that the increased GSK-3β activity in rats spinal cord neurons is involved in remifentanil-induced hyperalgesia.
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Comparative Study
Characterization of oxaliplatin-induced chronic painful peripheral neuropathy in the rat and comparison with the neuropathy induced by paclitaxel.
Anti-neoplastic agents in the platinum-complex, taxane, vinca alkaloid, and proteasome-inhibitor classes induce a dose-limiting, chronic, distal, symmetrical, sensory peripheral neuropathy that is often accompanied by neuropathic pain. Clinical descriptions suggest that these conditions are very similar, but clinical data are insufficient to determine the degree of similarity and to determine if they share common pathophysiological mechanisms. Animal models do not have the limitations of clinical studies and so we have characterized a rat model of chronic painful peripheral neuropathy induced by a platinum-complex agent, oxaliplatin, in order to compare it with a previously characterized model of chronic painful peripheral neuropathy induced by a taxane agent, paclitaxel. ⋯ Single fiber recordings found an abnormal incidence of A- and C-fibers with irregular, low-frequency spontaneous discharge. Prophylactic dosing with two drugs that are known to protect mitochondria, acetyl-l-carnitine and olesoxime, significantly reduced the development of pain hypersensitivity. Our results are very similar to those obtained previously with paclitaxel, and support the hypothesis that these two agents, and perhaps other chemotherapeutics, produce very similar conditions because they have a mitotoxic effect on primary afferent neurons.
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The peripheral serotonergic system has been implicated in the modulation of an array of pain states, from migraine to fibromyalgia; however, the mechanism by which serotonin (5HT) induces pain is unclear. Peripherally released 5HT induces thermal hyperalgesia, possibly via modulation of the transient receptor potential V1 (TRPV1) channel, which is gated by various noxious stimuli, including capsaicin. We previously reported in vitro that 5HT increases calcium accumulation in the capsaicin-sensitive population of sensory neurons with a corresponding increase in proinflammatory neuropeptide release, and both are antagonized by pretreatment with 5HT(2A) and 5HT(3) antagonists, as well as the anti-migraine drug sumatriptan. ⋯ We report that 5HT pretreatment enhances TRPV1-evoked thermal hyperalgesia, which is attenuated with local pretreatment with ketanserin, granisetron, or sumatriptan. We also report that peripheral 5HT induced a similar magnitude of thermal hyperalgesia in male and female rats. Overall, our results provide in vivo evidence supporting an enhancing role of 5HT on TRPV1-evoked thermal hyperalgesia, which can be attenuated by peripheral serotonergic intervention.
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Agonists for the cannabinoid CB2 receptor are antinociceptive in several rodent models and several reports have suggested that the target for these drugs is CB2 expressed in the spinal cord pain pathway. After confirming the efficacy of a systemically delivered CB2-selective agonist, GW405833, we tested this hypothesis by administering the CB2 agonists GW405833 and JWH-133, via intrathecal cannulation, to the lumbar spinal cord of rats that had undergone chronic constriction injury to induce mechanical allodynia. We found that although the non-selective CB1/CB2 cannabinoid receptor agonist WIN55,212-2 reversed mechanical allodynia in both ipsilateral and contralateral hind paws, neither GW405833 nor JWH-133 reversed mechanical allodynia. ⋯ Although protein-based analysis of CB2 partially matched the results of earlier studies using the same antibody, we found evidence that this antibody may be insufficiently specific for the detection of CB2 in native tissue. Using [(35)S]GTPγS binding assays, we found no evidence of functional CB2 in the spinal cord, in sham or surgery-treated tissue. However, WIN55,212-2 stimulated [(35)S]GTPγS binding showed clear evidence of functional CB1 receptors consistent with the known distribution of elements of the pain pathway, and we concluded that spinal CB2 receptors are not a likely target for cannabinoid-mediated antinociception in this model.
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Neuroscience letters · Feb 2012
The beta-lactam antibiotic, ceftriaxone, inhibits the development of opioid-induced hyperalgesia in mice.
The glutamate transporter GLT-1 is primarily responsible for glutamate clearance in the spinal cord. beta-Lactam antibiotics have been shown to attenuate neuropathic pain behaviors by promoting GLT-1 expression and function in the CNS. The present study tested the hypothesis that ceftriaxone, a prototype beta-lactam antibiotic, can prevent the development of opioid-induced hyperalgesia (OIH) in mice. ⋯ Correlating with the behavioral effects, ceftriaxone reversed downregulation of GLT-1 expression that was induced by OIH. These results suggest that ceftriaxone inhibited the development of OIH by up-regulating spinal GLT-1 expression.