Articles: hyperalgesia.
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Neuroscience letters · May 2017
Spinal dopaminergic involvement in the antihyperalgesic effect of antidepressants in a rat model of neuropathic pain.
Antidepressants such as tricyclic antidepressants, and serotonin noradrenaline reuptake inhibitors are a first-line treatment for neuropathic pain. Here, we aimed to determine the involvement of the spinal dopaminergic system in the antihyperalgesic effects of antidepressants in a rat model of neuropathic pain induced by spinal nerve ligation (SNL). The right L5 spinal nerve of male Sprague-Dawley rats was ligated under inhalation anesthesia to induce hyperalgesia. ⋯ Microdialysis revealed the dopamine levels in the spinal cord were increased after intraperitoneal injection of each antidepressant (10mg/kg). Furthermore, the dopamine content in homogenized spinal cord tissue were increased at 2 weeks after SNL and then subsequently declined. Our results suggest that the effect of antidepressants against neuropathic pain is related to modulation of not only noradrenalin and serotonin but also dopamine levels in the spinal cord.
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Metabotropic glutamate receptor 5 (mGluR5) activation in the infralimbic cortex (IL) induces pronociceptive behavior in healthy and monoarthritic rats. Here we studied whether the medullary dorsal reticular nucleus (DRt) and the spinal TRPV1 are mediating the IL/mGluR5-induced spinal pronociception and whether the facilitation of pain behavior is correlated with changes in spinal dorsal horn neuron activity. For drug administrations, all animals had a cannula in the IL as well as a cannula in the DRt or an intrathecal catheter. ⋯ Intrathecally administered TRPV1 antagonist prevented the IL/mGluR5-induced pronociception in both healthy and monoarthritic rats. The results suggest that the DRt is involved in relaying the IL/mGluR5-induced spinal pronociception in healthy control but not monoarthritic animals. Spinally, the IL/mGluR5-induced behavioral heat hyperalgesia is mediated by TRPV1 and associated with facilitated heat-evoked responses of WDR and NS neurons.
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In addition to inhibition of muscle and glandular hyperactivity, botulinum neurotoxin (BoNT) type A also interferes with pain processing. Previously, in a rat model of paclitaxel-induced polyneuropathy, abobotulinumtoxinA (aboBoNT-A) elicited analgesic effects not only in the injected paw, but also in the contralateral, non-injected paw. ⋯ The results expand evidence on bilateral analgesic effects of aboBoNT-A following unilateral administration across pain modalities, as the phenomenon is seen in more than one model of polyneuropathy as well as in a model of chronic inflammatory pain when the latter is rendered bilateral. The mechanism of bilateral analgesic effects of aboBoNT-A may require activation of the peripheral sensory neurons and involve retrograde axonal transport of the toxin into the spinal cord.
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Randomized Controlled Trial Comparative Study
Preoperative but Not Postoperative Flurbiprofen Axetil Alleviates Remifentanil Induced Hyperalgesia after Laparoscopic Gynecological Surgery: A Prospective, Randomized, Double-blinded, Trial.
Acute remifentanil exposure during intraoperative analgesia might enhance sensitivity to noxious stimuli and nociceptive responses to innocuous irritation. Cyclooxygenase inhibition was demonstrated to attenuate experimental remifentanil-induced hyperalgesia (RIH) in rodents and human volunteers. The study aimed to compare the effects of preoperative and postoperative flurbiprofen axetil (FA) on RIH after surgery. ⋯ Preoperative FA reduces postoperative RIH in patients undergoing laparoscopic gynecologic surgery under sevoflurane-remifentanil anesthesia.
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The complex regional pain syndrome (CRPS) is characterized by distal generalisation of pain beyond the initial trauma. This might be the result of impaired endogenous pain inhibition. ⋯ Conditioned pain modulation (CPM) is not impaired in the early phase of complex regional pain syndrome (CRPS) and neuralgia. Only in CRPS higher CPM was associated with lower cold pain thresholds.