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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Randomized Controlled Trial
Enlarged Areas of Pain and Pressure Hypersensitivityby Spatially Distributed Intramuscular Injections ofLow-Dose Nerve Growth Factor.
Intramuscular injection of nerve growth factor (NGF) causes muscle hyperalgesia without immediate pain. This double-blinded, randomized study assessed pain and muscle hypersensitivity after a single-site bolus NGF injection (5 µg) compared with 5 spatially distributed, low-dose NGF injections (1 µg, 4 cm distance) into the tibialis anterior (TA) muscles in 20 healthy subjects. Injection pain was rated on a visual analog scale. ⋯ Perspective: Spatially distributed low-dose NGF injections induced prolonged pain, mechanical muscle hypersensitivity, and enlarged contraction-evoked pain areas. These features mirror some clinical muscle pain conditions in which diffuse pain areas and muscle hypersensitivity are present during the activities of daily living. Low-dose NGF injections may be useful for further studies of prolonged pain conditions.
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Letter Case Reports
Erector Spinae Plane Block for Hyperalgesic Acute Pancreatitis.
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Reg Anesth Pain Med · May 2019
Ultrasound therapy reduces persistent post-thoracotomy tactile allodynia and spinal substance P expression in rats.
Therapeutic ultrasound (TU) alleviates nerve injury-associated pain, while the molecular mechanisms are less clear. This is an investigator-initiated experimental study to evaluate the mechanisms and effects of ultrasound on prolonged post-thoracotomy pain in a rodent model. ⋯ The results of this study suggest an increase in mechanical withdrawal thresholds and subcutaneous temperature, as well as a downregulation of spinal substance P and IL-1β, in the group which received ultrasound treatment. The regulation of spinal substance P and IL-1β may mediate potential effects of this non-invasive treatment.