Articles: hyperalgesia.
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A wide variety of human and animal experiments suggest that the anterior cingulate cortex (ACC) is one of the key brain substrates subserving higher order processing of noxious information. However, no sufficient data are now available regarding the mediation by ACC of different levels of pain processing as well as its potential descending modulation of spinal nociception. Using the well-developed rat bee venom (BV) model, the present study evaluated the effect of lesions of bilateral ACC on two levels of spontaneous nociceptive behaviors (spinally-processed persistent paw flinching reflex and supraspinally-processed paw lifting/licking) and heat or mechanical hypersensitivity under the inflammatory pain state. ⋯ Motor coordination, as measured by Rota-Rod treadmill test, was not impaired by bilateral ACC lesions. These results implicate that the ACC area of the brain plays differential roles in the mediation of different levels of spontaneous pain-related behaviors. The present study also provides additional evidence for the ACC-mediated descending facilitation of primary hyperalgesia (pain hypersensitivity) identified in the injured area under inflammatory pain state.
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In vivo experiments using a rat model of painful facet joint distraction. ⋯ Results suggest ligament tension may be required to produce pain from facet joint loading. Further studies of other cellular responses are needed to define the mechanisms of painful facet joint injury.
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Recently, we have reported that melittin, a major toxic peptide of the whole bee venom, plays a central role in production of local inflammation, nociception and hyperalgesia following the experimental honeybee's sting. However, the exact peripheral mechanisms underlying melittin-induced multiple pain-related behaviors are still less characterized. In the present study, we sought to investigate the potential roles of peripheral mitogen-activated protein kinases (MAPKs) in melittin-induced nociception and hyperalgesia by pre- and post-administration of three MAPK inhibitors, namely U0126 (1 mug, 10 mug) for extracellular signal-regulated kinase (ERK), SP600125 (10 mug, 100 mug) for c-Jun N-terminal kinase (JNK) and SB239063 (10 mug, 100 mug) for p38 MAPK, into the local inflamed area of one hind paw of rats. ⋯ Furthermore, local administration of the three compounds in naïve animals, respectively, did not change the basal pain sensitivity to either thermal or mechanical stimuli, suggesting lack of peripherally functional roles of the three MAPK subfamily members in normal pain sensitivity under the physiological state. Taken together, we conclude that activation of peripheral MAPKs, including ERK, JNK and p38, might contribute to the induction and maintenance of persistent ongoing pain and primary heat hyperalgesia in the melittin test. However, they are not likely to be involved in the processing of melittin-induced primary mechanical hyperalgesia, implicating a mechanistic separation between mechanical and thermal hyperalgesia in the periphery.
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The anti-inflammatory and analgesic properties of different bisphosphonates have been demonstrated in both animal and human studies. Ibandronate is a third-generation bisphosphonate effective in managing different types of bone pain. In this study we investigated its effects in a standard pre-clinical model of inflammatory pain. ⋯ On the other hand, the levels of PGE-2 in the inflamed hind-paw were unaffected by the administration of this bisphosphonate. Finally, ibandronate blocked the overexpression of SP mRNA in DRG induced by CFA-injection in the hind-paw. These data help to complete the pharmacodynamic profile of ibandronate, while also suggesting an involvement of several inflammatory mediators, with special reference to substance P, in the analgesic action of this bisphosphonate.
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Randomized Controlled Trial Clinical Trial
Analgesic and antihyperalgesic effects of nabilone on experimental heat pain.
In this study, we explored the analgesic and antihyperalgesic properties of a synthetic cannabinoid (nabilone) on experimental heat pain in men and women, as well as its effects on descending pain inhibitory systems. ⋯ Nabilone failed to produce analgesic effects and it did not interact with descending pain inhibitory systems. However, we found that a single 1 mg dose of nabilone reduced temporal summation for women but not men. Although a titration regime and a larger sample of subjects might have provided more robust effects, these preliminary results suggest that nabilone appears effective at relieving hyperalgesic responses in women. Possible neurobiological mechanisms and clinical implications are further discussed.