Articles: hyperalgesia.
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Human reproduction update · Nov 2015
ReviewWhat we know about primary dysmenorrhea today: a critical review.
Primary dysmenorrhea, or painful menstruation in the absence of pelvic pathology, is a common, and often debilitating, gynecological condition that affects between 45 and 95% of menstruating women. Despite the high prevalence, dysmenorrhea is often poorly treated, and even disregarded, by health professionals, pain researchers, and the women themselves, who may accept it as a normal part of the menstrual cycle. This review reports on current knowledge, particularly with regards to the impact and consequences of recurrent menstrual pain on pain sensitivity, mood, quality of life and sleep in women with primary dysmenorrhea. ⋯ Further study is needed to determine whether effectively blocking dysmenorrheic pain ameliorates risk for the development of chronic pain disorders and to explore whether it is possible to prevent the development-and not just treat-severe dysmenorrheic pain in adolescent girls. In conclusion, we demonstrate the extensive multi-factorial impact of dysmenorrhea and we encourage and direct researchers to necessary future studies.
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Mechanical allodynia, induced by normally innocuous low-threshold mechanical stimulation, represents a cardinal feature of neuropathic pain. Blockade or ablation of high-threshold, small-diameter unmyelinated group C nerve fibers (C-fibers) has limited effects on mechanical allodynia. Although large, myelinated group A fibers, in particular Aβ-fibers, have previously been implicated in mechanical allodynia, an A-fiber-selective pharmacological blocker is still lacking. ⋯ TLR5-mediated Aβ-fiber blockade, but not capsaicin-mediated C-fiber blockade, also reduced chemotherapy-induced ongoing pain without impairing motor function. Finally, flagellin/QX-314 co-application suppressed sodium currents in large-diameter human DRG neurons. Thus, our findings provide a new tool for targeted silencing of Aβ-fibers and neuropathic pain treatment.
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Elevated nerve growth factor (NGF) in the contralateral dorsal root ganglion (DRG) mediates mirror-image pain after peripheral nerve injury, but the underlying mechanism remains unclear. Using intrathecal injection of NGF antibodies, we found that NGF is required for the development of intra-DRG synapse-like structures made by neurite sprouts of calcitonin gene-related peptide (CGRP(+)) nociceptors and sympathetic axons onto neurite sprouts of Kv4.3(+) nociceptors. ⋯ Furthermore, neutralizing the neurotransmitter norepinephrine or CGRP in the synapse-like structures by antibodies has similar analgesic effect. Thus, elevated NGF after peripheral nerve injury induces neurite sprouting and the formation of synapse-like structures within the contralateral DRG, leading to the development of chronic mirror-image pain.
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Experimental neurology · Nov 2015
Phosphorylation of TRPV1 by cyclin-dependent kinase 5 promotes TRPV1 surface localization, leading to inflammatory thermal hyperalgesia.
Cyclin-dependent kinase 5 (Cdk5) is an important serine/threonine kinase that plays critical roles in many physiological processes. Recently, Cdk5 has been reported to phosphorylate TRPV1 at threonine 407 (Thr-407) in humans (Thr-406 in rats), which enhances the function of TRPV1 channel and promotes thermal hyperalgesia in the complete Freund's adjuvant (CFA)-induced inflammatory pain rats. However, the underlying mechanisms are still unknown. ⋯ Notably, intrathecal administration of the interfering peptide against the phosphorylation of Thr-406 alleviated heat hyperalgesia and reduced the surface level of TRPV1 in inflammatory pain rats. Together, these results demonstrate that Cdk5-mediated phosphorylation of TRPV1 at Thr-406 increases the surface level and the function of TRPV1, while the TAT-T406 peptide can effectively attenuate thermal hyperalgesia. Our studies provide a potential therapy for inflammatory pain.
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Randomized Controlled Trial
Movement Evoked Pain and Mechanical Hyperalgesia after Intramuscular Injection of Nerve Growth Factor: A Model of Sustained Elbow Pain.
Lateral epicondylalgia presents as lateral elbow pain provoked by upper limb tasks. An experimental model of elbow pain provoked by movement/muscle contraction and maintained over several days is required to better understand the mechanisms underlying sustained elbow pain. This study investigated the time course and pain location induced by nerve growth factor (NGF) injection into a wrist extensor muscle, and whether movement and muscle contraction/stretch provoked pain. ⋯ This article presents a novel experimental human pain model suitable to study the sustained effects of lateral elbow pain on sensorimotor function and to probe the mechanisms underlying persistent musculoskeletal pain.