Articles: hyperalgesia.
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We have recently described a novel form of hyperalgesic priming (type II) induced by agonists at two clinically important Gi-protein-coupled receptors (Gi-GPCRs), mu-opioid and A1-adenosine. Like mu-opioids, the antimigraine triptans, which act at 5-HT1B/D Gi-GPCRs, have been implicated in pain chronification. We determined whether sumatriptan, a prototypical 5-HT1B/D agonist, produces type II priming. ⋯ The prolongation of PGE2 hyperalgesia induced by sumatriptan was partially prevented by coinjection of antagonists for the 5-HT1B and 5-HT1D, but not 5-HT7, serotonin receptors and completely prevented by coadministration of a combination of the 5-HT1B and 5-HT1D antagonists. Moreover, the injection of selective agonists, for 5-HT1B and 5-HT1D receptors, also induced hyperalgesic priming. Our results suggest that sumatriptan, which signals through Gi-GPCRs, induces type I hyperalgesic priming, unlike agonists at other Gi-GPCRs, which induce type II priming.
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T-type Ca channels (T channels), particularly Cav3.2 among the 3 isoforms, play a role in neuropathic and visceral pain. We thus characterized the effects of RQ-00311651 (RQ), a novel T-channel blocker, in HEK293 cells transfected with human Cav3.1 or Cav3.2 by electrophysiological and fluorescent Ca signaling assays, and also evaluated the antiallodynic/antihyperalgesic activity of RQ in somatic, visceral, and neuropathic pain models in rodents. RQ-00311651 strongly suppressed T currents when tested at holding potentials of -65 ∼ -60 mV, but not -80 mV, in the Cav3.1- or Cav3.2-expressing cells. ⋯ The analgesic and antihyperalgesic/antiallodynic doses of oral and i.p. RQ did not significantly affect the locomotor activity and motor coordination. Together, RQ is considered a state-dependent blocker of Cav3.1/Cav3.2 T channels and may serve as an orally available analgesic for treatment of neuropathic and inflammatory pain including distinct visceral pain with minimum central side effects.
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Several mechanisms of remifentanil-induced hyperalgesia in spinal cord mainly have been explained such as N-methyl-D-aspartate receptors activation, but the mechanism in dorsal root ganglion (DRG) is poorly understood. It has been reported that CCL3 may be a regulator in both inflammatory pain and hyperalgesia. In this paper we explored whether CCL3 and CCR5, the mainly receptor of CCL3, play a role in the remifentanil-induced hyperalgesia in DRG by using a rat model with remifentanil administration. ⋯ The results highlighted the fact that CCL3 and its receptor CCR5 in DRG might contribute to remifentanil-induced hyperalgesia. Thus CCL3/CCR5 signaling may be further considered in the development of new therapeutic strategies.
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Randomized Controlled Trial
Effects of intraoperative high-dose vs low-dose remifentanil for postoperative epidural analgesia after gynecological abdominal surgery: a randomized clinical trial.
To evaluate whether intraoperative high-dose remifentanil infusion increased local anesthetic consumption in postoperative epidural analgesia and postoperative pain scores compared with low-dose remifentanil infusion. ⋯ Intraoperative high-dose remifentanil infusion increased local anesthetic consumption in postoperative epidural analgesia relative to low-dose remifentanil.
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Oxidative stress is generated in several peripheral nerve injury models. Nuclear factor erythroid 2-related factor 2 (Nrf2) is activated to have a role in antioxidant effect. After nerve injury, the severely painful behavior is also performed. ⋯ Therefore, in this study, we compared the effects of Nrf2 antibody administration following sciatic nerve-pinch injury on painful behavior induced in young mice and neurochemical changes in dorsal root ganglion neurons. After pinch nerve injury, we found that the magnitude of the thermal allodynia was significantly decreased after application of Nrf2 antibody (5ul, 1mg/ml) in such injured animals and phosphorylated ERK(p-ERK) as well as the apoptotic protein (i.e., Bcl-6) in DRG neurons were also down-regulated in the anti-Nrf2-treated injured groups compared to the saline-treated groups. Taken collectively, these data suggested that the Nrf2 antibody reduced thermal hyperalgesia via ERK pathway and the down regulation of Bcl-6 protein from the apoptosis pathway might be protecting against the protein deletions caused by anti-Nrf2 effect and suggested the new therapeutic strategy with Nrf2 inhibitor following nerve injury.