Articles: hyperalgesia.
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Randomized Controlled Trial
Tropisetron blocks analgesic action of acetaminophen: a human pain model study.
Because the mechanism underlying the analgesic action of acetaminophen remains unclear, we investigated the possible interaction of acetaminophen with central serotonergic pathways. The effects of acetaminophen, tropisetron, the combination of both drugs, and saline on pain perception and central sensitization in healthy volunteers were compared. Sixteen healthy volunteers were included in this randomized, double-blind, placebo-controlled crossover study. ⋯ In summary, while the combination of acetaminophen and tropisetron showed no analgesic action, each drug administered alone led to decreased pain ratings as compared to saline. In an electrically evoked human pain model, the combination of acetaminophen with tropisetron was free of any analgesic potential. However, when administered on its own, both acetaminophen and tropisetron were mildly analgesic.
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Sensory gain (i.e., hyperalgesia) and sensory loss (ie, hypoalgesia) are key features of neuropathic pain syndromes. Previously, we showed that conditioning electrical stimuli may provoke either sensory gain or decline in healthy subjects, depending on the stimulation frequencies applied. In the present study we sought to determine whether sensory decline induced by 20-Hz electrical stimulation preferentially of peptidergic C-nociceptors induces antihyperalgesic effects in a transdermal electrical pain model. ⋯ We conclude that 20-Hz noxious electrical stimulation may represent a neurostimulatory paradigm with antihyperalgesic properties. These findings may thus be of relevance for the future therapy of neuropathic pain syndromes as well. Sensory decline induced by 20-Hz electrical stimulation of peptidergic C-nociceptors induces antihyperalgesic effects in a transdermal electrical pain model.
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Electrical stimulation of the primary motor cortex has been used since 1991 to treat chronic neuropathic pain. Since its inception, motor cortex stimulation (MCS) treatment has had varied clinical outcomes. Until this point, there has not been a systematic study of the stimulation parameters that most effectively treat chronic pain, or of the mechanisms by which MCS relieves pain. ⋯ We also find that stimulation of the ZI mimics the effects of MCS and that reversible inactivation of ZI blocks the effects of MCS. These findings suggest that the reduction of hyperalgesia may be due to MCS effects on ZI. In an animal model of central pain syndrome, motor cortex stimulation reduces hyperalgesia by activating zona incerta and therefore restoring inhibition in the thalamus.
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Pressure algometry is used for assessment of pain sensitivity. In this study the relation between tissue characteristics and pressure pain thresholds was investigated. ⋯ The pressure pain sensitivity of the deep layer is related to the amount of muscle strain, which is affected by the muscle hardness and the thickness of adipose tissue. This is clinically relevant as these two factors are not taken into consideration when pressure pain assessments are performed in clinical routine.
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The aim of this study was to analyze cutaneous pain threshold (CPT) during the interictal phase in headache patients, and the relationships between headache frequency and analgesic use. A consecutive series of 98 headache patients and 26 sex- and age-balanced controls were evaluated. Acute allodynia (AA) was assessed by Jakubowski questionnaire, and interictal allodynia (IA) by a skin test with calibrated monofilaments. ⋯ In MOH patients there were no significant differences depending on the diagnosis of starting headache (migraine or tension type headache) and, in both groups, we found the overuse of analgesics plays an important role: intake of more than one daily drug dramatically reduces the CPT (p < 0.05). Thus, when acute allodynia increases frequency, worsens or appears for the first time in patients with a long-standing history of chronic headache, it could reasonably suggest that the reduction of CPT had started, without using a specific practical skin test but simply by questioning clinical headache history. In conclusion, these results indicate that the role of medication overuse is more important than chronicization in lowering CPT, and suggest that prolonged periods of medication overuse can interfere with pain perception by a reduction of the pain threshold that facilitates the onset of every new attack leading to chronicization.