Articles: hyperalgesia.
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Prolactin (PRL) is a hormone and a neuromodulator. It sensitizes TRPV1 (transient receptor potential cation channel subfamily V member 1) responses in sensory neurons, but it is not clear whether peripheral inflammation results in the release of endogenous PRL, or whether endogenous PRL is capable of acting as an inflammatory mediator in a sex-dependent manner. To address these questions, we examined inflammation-induced release of endogenous PRL, and its regulation of thermal hyperalgesia in female and male rats. ⋯ In contrast, PRL contributed to inflammatory thermal hyperalgesia in intact male rats at 24, but not at 6 h. These findings indicate that inflammation leads to accumulation of endogenous PRL in female and male rats. Furthermore, PRL acts as an inflammatory mediator at different time points for female and intact male rats.
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Anesthesia and analgesia · Sep 2011
Hyperbaric oxygenation therapy alleviates chronic constrictive injury-induced neuropathic pain and reduces tumor necrosis factor-alpha production.
The development of hyperalgesia and allodynia after chronic constrictive injury (CCI) is associated with significantly increased tumor necrosis factor (TNF)-α and interleukin (IL)-1β. Theoretically, if the production of TNF-α and/or IL-1β could be reduced, neuropathic pain syndrome may be alleviated. Recently, a beneficial effect of hyperbaric oxygenation therapy (HBOT) in the treatment of pain disorders has been suggested. Our present study was designed to examine the hypotheses that (1) CCI-induced neuropathic pain may be associated with increased production of TNF-α and IL-1β, (2) HBOT may alleviate CCI-induced neuropathic pain, and (3) the alleviated neuropathic pain may be associated with reduced production of TNF-α and/or IL-1β. ⋯ These data show that HBOT alleviates CCI-induced neuropathic pain and inhibits endoneuronal TNF-α production, but not IL-1β in CCI-induced neuropathic pain. Reduced TNF-α production may, at least in part, contribute to the beneficial effect of HBOT.
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Stress exacerbates both experimental and clinical pain, most well-characterized in irritable bowel and fibromyalgia syndromes. Since it has been hypothesized that cytokines play an etiopathogenic role in fibromyalgia and other chronic widespread pain conditions, we investigated the relationship between stress and cytokines in a model of stress-induced chronic somatic pain. ⋯ LPS-induced hyperalgesia was significantly greater in stressed rats, but when rats were treated intrathecally with antisense oligodeoxynucleotide (ODN), to decrease either the gp130 subunit of the IL-6 receptor or the TNFα receptor, in nociceptors, skeletal muscle hyperalgesia in sound stressed, but not control, rats was prevented. These data suggest that chronic stress alters signaling in the primary afferent nociceptor for the hyperalgesia induced by endogenously produced pro-inflammatory cytokines.
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Anesthesia and analgesia · Sep 2011
A new animal model of trigeminal neuralgia produced by administration of cobra venom to the infraorbital nerve in the rat.
Understanding the mechanism of trigeminal neuralgia may be elucidated by developing laboratory animal models that closely mimic the features of this specific type of neuropathic pain. We have developed an experimental animal model for trigeminal neuralgia using a technique of injecting cobra venom into the infraorbital nerve (ION) trunk. ⋯ The cobra venom model may provide a reasonable model for investigating the mechanism of trigeminal neuropathic pain.
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Anesthesia and analgesia · Sep 2011
The median effective dose of ketamine and gabapentin in opioid-induced hyperalgesia in rats: an isobolographic analysis of their interaction.
Ketamine and gabapentin have been shown to prevent the delayed hyperalgesia induced by short-term use of systemic opioids. The mechanism of this action is believed to be likely at the spinal level, through an antagonism of the N-methyl-D-aspartate receptors for ketamine, and through a specific binding site for gabapentin. In this study, we sought to determine the nature of the interaction of these 2 mechanistically distinct antihyperalgesic drugs in a model of opioid-induced hyperalgesia in rats. The median effective antihyperalgesic doses of each drug and of their combination were first defined, to assess the nature of the interaction using an isobolographic analysis. ⋯ The isobolographic analysis demonstrated that the combination of the 2 drugs produces effective antihyperalgesia with a supraadditive (synergistic) action.