Articles: hyperalgesia.
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No study has previously analyzed pressure pain sensitivity of nerve trunks in migraine. This study aimed to examine the differences in mechanical pain sensitivity over specific nerves between patients with unilateral migraine and healthy controls. ⋯ In patients with unilateral migraine, we found increased mechano-sensitivity of the supra-orbital nerve on the symptomatic side of the head. Outside the head, the same patients showed increased mechano-sensitivity of the main peripheral nerves of both upper limbs, without asymmetries. Such diffuse hypersensitivity of the peripheral nerves lends further evidence to the presence of a state of hyperexcitability of the central nervous system in patients with unilateral migraine.
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Previous studies on pressure pain sensitivity in patients with migraine have shown conflicting results. There is emerging evidence suggesting that pain sensitivity is not uniformly distributed over the muscles, indicating the existence of topographical changes in pressure pain sensitivity. The aim of this study was to calculate topographical pressure pain sensitivity maps of the temporalis muscle in a blind design in patients with strictly unilateral migraine compared with controls. ⋯ Within the migraine group, PPT levels were decreased bilaterally from the posterior to the anterior column of the temporalis muscle (Student-Newman- Keuls analysis; P < 0.05), with the most sensitive in the anterior part of the muscle. For controls, PPT did not follow such anatomical distribution, the most sensitive point being the centre of the mid-muscle belly. This study showed bilateral sensitization to pressure in unilateral migraine, suggesting the involvement of central components.
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The aim of this study was to investigate whether bilateral widespread pressure hypersensitivity exists in patients with unilateral carpal tunnel syndrome. A total of 20 females with carpal tunnel syndrome (aged 22-60 years), and 20 healthy matched females (aged 21-60 years old) were recruited. Pressure pain thresholds were assessed bilaterally over median, ulnar, and radial nerve trunks, the C5-C6 zygapophyseal joint, the carpal tunnel and the tibialis anterior muscle in a blinded design. ⋯ Our findings revealed bilateral widespread pressure hypersensitivity in subjects with carpal tunnel syndrome, which suggest that widespread central sensitization is involved in patients with unilateral carpal tunnel syndrome. The generalized decrease in pressure pain thresholds associated with pain intensity and duration of symptoms supports a role of the peripheral drive to initiate and maintain central sensitization. Nevertheless, both central and peripheral sensitization mechanisms are probably involved at the same time in carpal tunnel syndrome.
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Previous data indicate that morphine-6beta-glucuronide (M6G), a morphine metabolite with analgesic properties, can paradoxically increase pain sensitivity in mice and humans. The authors tested mice and humans for M6G hyperalgesia and assessed the contribution of N-methyl-D-aspartate receptor activity in mice. ⋯ These data indicate that M6G causes hyperalgesia independent of previous or concurrent opioid receptor activity or analgesia. In mice, a causal role for the N-methyl-D-aspartate receptor is also indicated.
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Can. J. Physiol. Pharmacol. · Jun 2009
URB597, an inhibitor of fatty acid amide hydrolase, reduces hyperalgesia in diabetic rats.
Diabetic rats display increased pain responses after injection of formalin into the paw or thermal stimulation of the tail, suggesting the presence of hyperalgesia. In this study, we investigated the efficacy of URB597 (0.1, 0.3, and 0.5 mg/kg, i.p.), an inhibitor of endocannabinoids metabolism, on 2 models of experimental hyperalgesia in streptozotocin (STZ)-induced diabetic rats. Animals were divided into control, URB597-treated control (0.1, 0.3, and 0.5 mg/kg), diabetic, and URB597-treated diabetic (0.1, 0.3, and 0.5 mg/kg) groups. ⋯ URB597 treatment did not affect body weight or plasma glucose level of treated animals compared with nontreated animals. This study shows that increasing endocannabinoid neurotransmission with URB597 displays efficacy in chemical and thermal models of diabetic hyperalgesia. It also suggests that URB597 is a promising tool for treatment of painful diabetic neuropathy.