Articles: hyperalgesia.
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Trigeminal and cervical afferents converge on neurons of the trigeminocervical complex and may significantly alter the function of these neurons. This interaction may have implications for the pathophysiology and treatment of primary headache disorders. Therefore, the aim of this work was to study pain modulatory mechanisms within the trigeminocervical complex. ⋯ Trigeminal nociception stayed unchanged despite of occipital costimulation.
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Neurobiology of disease · Jul 2016
Reversal of neurochemical alterations in the spinal dorsal horn and dorsal root ganglia by Mas-related gene (Mrg) receptors in a rat model of spinal nerve injury.
The rodent Mas-related gene (Mrg) receptor subtype C has been demonstrated to inhibit pathological pain. This study investigated the mechanisms underlying the reversal of pain hypersensitivity by the selective MrgC receptor agonist bovine adrenal medulla 8-22 (BAM8-22) in a rat model of L5 spinal nerve ligation (SNL). Intrathecal (i.t.) administration of BAM8-22 (0.1-10nmol) attenuated mechanical allodynia in a dose-dependent manner on day 10 after SNL. ⋯ Furthermore, the BAM8-22 exposure suppressed the lipopolysaccharide (LPS)-induced increase of nNOS and IL-1β in the DRG explant cultures and the BAM8-22-induced suppression disappeared in the presence of MrgC receptor antibody. The present study provides evidence that activation of MrgC receptors inhibits nerve injury-induced increase of pronociceptive molecules in DRG neurons, suppressing astrocyte activation, the upregulation of excitatory mediators and phosphorylation of transcription factors in the spinal dorsal horn. As MrgC receptors are unequally expressed in the dorsal root and trigeminal ganglia, this study suggests that targeting MrgC receptors could be a new therapy for neuropathic pain with limited unwanted effects.
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Alcohol. Clin. Exp. Res. · Jul 2016
Randomized Controlled TrialEffect of Intravenous Ethanol on Capsaicin-Induced Hyperalgesia in Human Subjects.
The objective of this study was to assess ethanol's (EtOH's) effects on capsaicin-induced hyperalgesia in healthy participants. Specifically, we investigated the change in area of capsaicin-induced hyperalgesia following 3 interventions: intravenous EtOH at 2 targeted breath alcohol concentrations (BrAC), or placebo. ⋯ In a human model examining pain phenomena related to central sensitization, this study is the first to demonstrate that capsaicin-induced hyperalgesia is markedly attenuated by EtOH. The capsaicin experimental pain paradigm employed provides a novel approach to evaluate EtOH's effects on pain processing. The antihyperalgesic effects of EtOH observed have important clinical implications for the converging fields of substance abuse and pain medicine and may inform why patients with chronic pain often report alcohol use as a form of self-medication.
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Allodynia reflects the clinical correlate of central sensitization, but it is usually neglected in clinical headache management. We aimed to report the prevalence and previously unnoticed associations of allodynia in migraineurs by a nationwide face-to-face questionnaire-based study by physicians. ⋯ The duration, severity, and disability of migraine attacks, photophobia, phonophobia, and osmophobia, as well as premonitory signs, showed significant associations with allodynia in the general population. Moreover, migraineurs with aura or family history of migraine more often reported allodynia, and allodynic migraneurs were more sensitive to hormonal changes. Allodynia, which seems to indicate higher tendency to central sensitization, should be implemented in daily headache practice to predict the prognosis and high levels of migraineous involvement.
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Pain biomarkers are warranted for individualized pain management. Based on different pain modulatory phenotypes, the objectives of this study were to explore the existence of subgroups within patients with nonmalignant chronic pain and to investigate differences in clinical pain and pain hypersensitivity between subgroups. Cuff algometry was performed on lower legs in 400 patients with chronic pain to assess pressure pain threshold, pressure pain tolerance, temporal summation of pain (TSP: increase in pain scores to 10 repeated stimulations), and conditioned pain modulation (CPM: increase in cuff pressure pain threshold during cuff pain conditioning on the contralateral leg). ⋯ Moreover, group 1 demonstrated higher clinical pain scores than group 4 (P < 0.05). Although not different between subgroups, patients were profiled on demographics, disability, pain catastrophizing, and fear of movement. Future research should investigate interventions tailored towards these subgroups.