Articles: hyperalgesia.
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P2X(7) receptor is an important member of ATP-sensitive ionotropic P2X receptors family, which includes seven receptor subtypes (P2X(1)-P2X(7)). Recent evidence indicates that P2X(7)R participates in the onset and persistence of neuropathic pain. In tetanic stimulation of the sciatic nerve model, P2X(7)R was involved in the activation of microglia, but whether this happens in other neuropathic pain models remains unclear. ⋯ Intrathecal administration of the P2X(7)R antagonist Brilliant Blue G (BBG) reversed CCI-induced mechanical allodynia and thermal hypersensitivity. Double-labeled immunofluorescence showed that P2X(7)R expression were restricted to microglia, spinal microglia were activated after nerve injury, which was inhibited by BBG. These results indicated that spinal P2X(7)R mediate microglia activation, this process may play an important role in development of mechanical allodynia and thermal hypersensitivity in CCI model.
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Randomized Controlled Trial
Test order of quantitative sensory testing facilitates mechanical hyperalgesia in healthy volunteers.
Quantitative sensory testing (QST) has become a widely used method to evaluate different submodalities of the somatic sensory system (predominantly) in patients with neuropathic pain. QST consists of 7 tests measuring 13 parameters in order to assess and quantify the perception of temperature, touch, pain, pressure, and vibration. The German Research Network on Neuropathic Pain implemented a standardized QST protocol including a defined testing order of the measurements. Accordingly, subjects tested with QST undergo thermal before mechanical testing. In the present study, we investigated the effect of testing order on the results of QST. Twenty healthy subjects were tested twice, 1 week apart with 2 different QST testing orders: the standardized testing order according to the German Research Network on Neuropathic Pain and a modified testing order in which mechanical stimuli were applied before thermal stimuli. For the test protocol that began with thermal testing, subjects exhibited signs of an increased mechanical perception: The mechanical pain sensitivity was significantly increased (P = .001, Wilcoxon test) for each pinprick stimulator and the mechanical pain threshold was lowered by a factor of 2 when compared with the modified testing order in which mechanical parameters were tested at the beginning of the session without prior thermal stimulation. Thermal parameters were the same for both test-order paradigms. These data indicate that preceding mild thermal stimulation might lead to a sensitization to mechanical stimuli and thus to mechanical hyperalgesia. Alternative habituation mechanisms in the modified testing order resulting from repeated pinprick stimulation at the beginning should also be debated. QST is a helpful diagnostic tool but interpretation should be done with consideration of interaction between test parameters. Reference data are only valid in the testing order from which they are obtained. ⋯ Present data showed that mechanical hyperalgesia followed thermal testing. This article demonstrates that the test order of quantitative sensory testing is relevant in interpreting the results obtained. Reference values are suitable in the test order from which they are obtained.
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Randomized Controlled Trial
[The role of magnesium in preventing postoperative hyperalgesia].
Intraoperative remifentanil administration results in acute opioid tolerance that is manifested by increased postoperative pain, opioid requirement and specifically periincisional hyperalgesia. The aim of this study was to investigate the effect of magnesium in preventing remifentanil-induced hyperalgesia. ⋯ Magnesium administered preemptively reduced remifentanil-induced hyperalgesia.
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This study evaluated the effectiveness of a single fixed-dose tablet of sumatriptan 85 mg/naproxen sodium 500 mg (sumatriptan-naproxen) using a very early treatment paradigm in migraine patients whose attacks were historically accompanied by cutaneous allodynia. ⋯ In this open-label study, allodynic patients reported that their migraine attacks responded well and they achieved a high degree of satisfaction following treatment with a fixed-dose tablet of sumatriptan 85 mg/naproxen sodium 500 mg administered in a very early treatment paradigm.
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Trigeminal neuropathic pain is a facial pain syndrome associated with trigeminal nerve injury. However, the mechanism of trigeminal neuropathic pain is poorly understood. This study aimed to determine the role of transient receptor potential vanilloid 1 (TRPV1) in heat hyperalgesia in a trigeminal neuropathic pain model. ⋯ Capsazepine suppressed heat hyperalgesia but not mechanical allodynia. The number of TRPV1-positive neurons in the trigeminal ganglia was significantly increased in the large-diameter-cell group. These results suggest that TRPV1 plays an important role in the heat hyperalgesia observed in the pIONL model.