Articles: hyperalgesia.
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The cellular and molecular pathophysiological mecha\nisms of pain processing in neglected parasitic infections such as leishmaniasis remain unknown. The present study evaluated the participation of spinal cord glial cells in the pathophysiology of pain induced by Leishmania amazonensis infection in BALB/c mice. ⋯ L. amazonensis skin infection produces chronic pain by central mechanisms involving spinal cord astrocytes and microglia-related production of cytokines and chemokines, and NFκB activation contributes to L. amazonensis infection-induced hyperalgesia and neuroinflammation.
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Neuropathic pain can develop after nerve injury, leading to a chronic condition with spontaneous pain and hyperalgesia. Pain is typically restricted to the side of the injured nerve, but may occasionally spread to the contralateral side, a condition that is often referred to as mirror-image pain. Mechanisms leading to mirror-image pain are not completely understood, but cannabinoid CB2 receptors have been implicated. ⋯ This behavioral pain phenotype was accompanied by an increased staining of microglia in the dorsal horn of the spinal cord, as evidenced by an enhanced Iba 1 expression [CB2KO, p = 0.0175; CB2-LysM, p = 0.0425]. Similarly, myeloid-selective knockouts showed an increased expression of the leptin receptor in the injured ipsilateral sciatic nerve, thus further supporting the notion that leptin signaling contributes to the increased neuropathic pain responses of CB2 receptor knockout mice. We conclude that CB2 receptors on microglia and macrophages, but not on neurons, modulate neuropathic pain responses.
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Opioid-induced hyperalgesia (OIH) is a phenomenon that causes an increased pain sensitization and perception of pain to noxious stimuli secondary to opioid exposure. While this clinical effect has been described in the surgical setting, it is unclear if OIH occurs in the nonsurgical setting. ⋯ Most included studies identified OIH as a significant outcome within the nonsurgical setting. However, due to conflicting conclusions and various limitations, the clinical impact of OIH could not be assessed. Clinicians should monitor for effects of OIH in the nonoperative setting because there is insufficient evidence from the available literature to conclude that OIH is consistently observed in this setting.
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Letter Case Reports
Erector Spinae Plane Block for Hyperalgesic Acute Pancreatitis.
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Pain models are commonly used in drug development to demonstrate analgesic activity in healthy subjects and should therefore not cause long-term adverse effects. The ultraviolet B (UVB) model is a model for inflammatory pain in which three times the minimal erythema dose (3MED) is typically applied to induce sensitization. Based on reports of long-lasting postinflammatory hyperpigmentation (PIH) associated with 3MED, it was decided to investigate the prevalence of PIH among subjects who were previously exposed to 3MED at our research centre. In addition, re-evaluation of the UVB inflammation model using a reduced exposure paradigm (2MED) was performed in healthy subjects. ⋯ Postinflammatory hyperpigmentation is an unwanted long-term side effect associated with the UVB inflammation model using the 3× minimal erythema dose (3MED) paradigm. In contrast, using a 2MED paradigm results in hyperalgesia that is stable for 36 hr and has a lower risk of inducing postinflammatory hyperpigmentation.