Articles: hyperalgesia.
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We have demonstrated that the activation of P2X3 receptor on peripheral afferent neurons is critical to development of inflammatory hyperalgesia in peripheral tissue, although pharmacological administration of prostaglandin E(2) or sympathomimetic amines is enough to sensitize primary afferent neurons by acting directly in neuronal receptors. Therefore, to clarify this ambiguity this study verifies whether P2X3 receptor activation on primary afferent neurons enables the sensitization induced by prostaglandin E(2) or sympathomimetic amine. ⋯ Furthermore, because PKCɛ translocation induces an increase of neuronal susceptibility to inflammatory mediators, this study demonstrates that αβmeATP in peripheral tissue increases the expression of PKCɛ in cell membranes of DRG-L5, and in contrast, the administration of PKCɛ translocation inhibitor (1 μg/paw) in peripheral tissue 45 min before αβmeATP, prevented the hyperalgesia induced by sub-threshold dose of PGE(2) (4 ng/paw). In conclusion, this study suggests that neuronal P2X3 receptor activation and the consequent PKCɛ translocation increase the susceptibility of nociceptor to inflammatory mediators allowing the development of inflammatory hyperalgesia.
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Biomedical research · Apr 2013
Effects of repeated milnacipran and fluvoxamine treatment on mechanical allodynia in a mouse paclitaxel-induced neuropathic pain model.
Paclitaxel is widely used in cancer chemotherapy for the treatment of solid tumors, but it frequently causes peripheral neuropathy. Milnacipran, a serotonin/noradrenaline reuptake inhibitor and fluvoxamine, a selective serotonin reuptake inhibitor, have shown efficacy against several chronic pain syndromes. In this study, we investigated the attenuation of paclitaxel-induced mechanical allodynia in mice by milnacipran and fluvoxamine. ⋯ However, repeated administration of milnacipran (10, 20 mg/kg, once per day, i.p.) for 5 days significantly reduced paclitaxel-induced mechanical allodynia. In contrast, repeated fluvoxamine administration (40 mg/kg, once per day, i.p.) for 5 days resulted in a weak attenuation of paclitaxel-induced mechanical allodynia. These results suggest that chronic paclitaxel administration induces mechanical allodynia, and that repeated milnacipran administration may be an effective therapeutic approach for the treatment of neuropathic pain caused by paclitaxel treatment for cancer.
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The phosphorylation of p38 mitogen-activated protein kinase (MAPK) in the dorsal root ganglion (DRG) promotes primary afferent sensitization. The role of p38MAPK signaling in the DRG in the pathogenesis of plantar incision hyperalgesia has not been investigated. ⋯ p38MAPK signaling in the DRG plays a crucial role in the development of primary afferent sensitization and pain behavior caused by plantar incision.
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Peripheral neuropathy is a common complication of diabetes and is often accompanied by episodes of pain. There is evidence that diabetic neuropathy may affect the trigeminal nerve, altering the transmission of orofacial sensory information. Structural changes in the trigeminal ganglia may be involved in the development of these sensory alterations. ⋯ Pregabalin treatment (30mg/kg, p.o.) of diabetic rats resulted in marked and prolonged (up to 6h) reduction of heat and cold orofacial hyperalgesia. Likewise, morphine treatment (2.5mg/kg, s.c.) abolished orofacial heat and cold hyperalgesia, but its effect was significant only up to 1h after the administration. In conclusion, the results of the present study demonstrated that streptozotocin-treated rats developed long-lasting orofacial heat and cold hyperalgesia, which is more amenable to reduction by pregabalin than morphine.
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Chronic musculoskeletal pain is a significant health problem and is associated with increases in pain during acute physical activity. Regular physical activity is protective against many chronic diseases; however, it is unknown if it plays a role in development of chronic pain. The current study induced physical activity by placing running wheels in home cages of mice for 5 days or 8 wk and compared these to sedentary mice without running wheels in their home cages. ⋯ We demonstrate that regular physical activity prevents the development of chronic muscle pain and exercise-induced muscle pain by reducing phosphorylation of the NR1 subunit of the NMDA receptor in the central nervous system. However, regular physical activity has no effect on development of acute pain. Thus physical inactivity is a risk factor for development of chronic pain and may set the nervous system to respond in an exaggerated way to low-intensity muscle insults.