Articles: hyperalgesia.
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Damage on one side of the body can also result in pain on the contralateral unaffected side, called mirror-image pain (MIP). Currently, the mechanisms responsible for the development of MIP are unknown. In this study, we investigated the involvement of spinal microglia and interleukin-1β (IL-1β) in the development of MIP using a peripheral inflammatory pain model. ⋯ However, i.t. pretreatment with fluorocitrate, an astrocyte inhibitor, restored minocycline- or IL-1ra-induced contralateral MA. These results suggest that spinal IL-1β derived from activated microglia temporarily suppresses astrocyte activation, which can ultimately prevent the development of contralateral MA under inflammatory conditions. These findings imply that microglial IL-1β plays an important role in regulating the induction of inflammatory MIP.
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Decreased spinal cord GABAergic inhibition is a major contributor to the persistent neuropathic pain that can follow peripheral nerve injury. Recently, we reported that restoring spinal cord GABAergic signaling by intraspinal transplantation of cortical precursors of GABAergic interneurons from the embryonic medial ganglionic eminence (MGE) can reverse the mechanical hypersensitivity (allodynia) that characterizes a neuropathic pain model in the mouse. ⋯ Transplants from these mice, in which GABA is synthesized but cannot be stored or released, had no effect on mechanical hypersensitivity or heat hyperalgesia in the paclitaxel model. Taken together, these results demonstrate the therapeutic potential of GABAergic precursor cell transplantation in diverse neuropathic pain models and support our contention that restoration of inhibitory controls through release of GABA from the transplants is their mode of action.
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J Pain Palliat Care Pharmacother · Jun 2015
ReviewFentanyl-induced hyperalgesia in acute pain management.
There are safety concerns with the use of fentanyl, including respiratory depression, nausea, constipation, and possibly opioid-induced hyperalgesia (OIH). The purpose of this review is to evaluate the occurrence and significance of opioid-induced hyperalgesia (OIH) after acute fentanyl exposure. A literature search was conducted from October 1995 through January 2015 using MEDLINE, Embase, and Scopus with the terms hyperalgesia, fentanyl, pronociceptive, acute tolerance, and acute. ⋯ The data on OIH after acute fentanyl exposure are limited and conflicting. Hyperalgesia should be considered in patients with uncontrolled pain despite escalating fentanyl doses, since the possibility of fentanyl-induced OIH exists in the acute setting. Well-designed trials are needed to determine the clinical significance of this phenomenon.
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Anesthesia and analgesia · Jun 2015
Mitigation of Experimental, Chronic Post-Thoracotomy Pain by Preoperative Infiltration of Local Slow-Release Bupivacaine Microspheres.
Postoperative pain is treated incompletely and ineffectively in many circumstances, and chronic postoperative pain causes suffering and diminishes productivity. The objective of this project is to determine whether a recently developed slow-release formulation of bupivacaine was effective in reducing the experimental chronic postoperative pain. ⋯ Local slow release of bupivacaine subcutaneously from the MS-Bupi formulation suppresses postoperative mechanical hypersensitivity for ≥4 weeks after experimental thoracotomy. Systemic bupivacaine from this treatment has no effect on this hypersensitivity.
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Patients receiving chronic opioid treatment who develop paradoxical pain sensations, as well as worsening existing pain, can be diagnosed as suffering from opioid-induced hyperalgesia (OIH). As the worldwide population expands so too does the proportion of patients who experience pain that requires a strong opioid. Recognizing the symptoms of OIH and optimizing the use of morphine in the hospital setting is imperative. This review focuses on clinical data relating to evidence of OIH at the bedside and the novel techniques employed by healthcare providers in order to improve the heightened pain sensations experienced by susceptible patients. ⋯ Looking to the future, improved clinician-patient communication, advanced diagnostic techniques and a refinement of prescribed adjunct pharmacotherapies will offer the most successful multimodal pain management approach to the problem of OIH.