Pain
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Comparative Study
Sensory and motor effects of experimental muscle pain in patients with lateral epicondylalgia and controls with delayed onset muscle soreness.
This study compares the effect of experimental muscle pain on deep tissue sensitivity and force attenuation in the wrist extensors of patients with lateral epicondylalgia (n=20), and healthy controls (n=20) with experimentally induced sensori-motor characteristics simulating lateral epicondylalgia. Delayed onset muscle soreness (DOMS) in wrist extensors of healthy controls was induced by eccentric exercise in one arm 24h prior to injection (Day 0). Saline-induced pain intensity (visual analogue scale, VAS), distribution, and quality were assessed quantitatively in both arms for both groups. ⋯ Patients demonstrated significant bilateral hyperalgesia at extensor carpi radialis brevis during and post saline-induced pain compared to pre-injection and healthy controls (P<0.04). The sore arm in patients and the DOMS arms in healthy subjects showed significantly reduced maximal force (P<0.0001), at all Day 1 times compared with the control arms. In patients, the bilateral increase in deep tissue sensitivity and enlarged referred pain areas during saline-induced pain might suggest involvement of central sensitisation.
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Activation of extracellular signal-regulated kinase (ERK), a mitogen activated-protein kinase (MAPK), in dorsal horn neurons contributes to inflammatory pain by transcription-dependent and -independent means. We have now investigated if ERK is activated in the spinal cord after a spinal nerve ligation (SNL) and if this contributes to the neuropathic pain-like behavior generated in this model. An L5 SNL induces an immediate (<10 min) but transient (<6 h) induction of phosphoERK (pERK) restricted to neurons in the superficial dorsal horn. ⋯ Intrathecal injection of the MEK (ERK kinase) inhibitor PD98059 on Day 2, 10 or 21 reduces SNL-induced mechanical allodynia. Our results suggest that ERK activation in the dorsal horn, as well as in the DRG, mediates pain through different mechanisms operating in different cells at different times. The sequential activation of ERK in dorsal horn microglia and then in astrocytes might reflect distinct roles for these two subtypes of glia in the temporal evolution of neuropathic pain.
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Effective verbalization of pain requires progressive cognitive development and acquisition of social communication skills. Use of self-report in pediatric pain assessment assumes children have acquired a capacity to understand and use common words to describe pain. The current investigation documented the language most commonly used by young children to describe pain and the age of onset of use of these words. ⋯ The word-stem 'pain' was used relatively infrequently and gradually emerged in children's vocabularies. The findings indicate that young children rely on a select number of words to describe pain, with these words appearing in children's vocabularies at an early age. These results have implications for developmentally appropriate pain assessment in young children.
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Comparative Study
Relationship between pain symptoms and referred sensory and trophic changes in patients with gallbladder pathology.
The relationship was investigated between algogenic potential of gallbladder pathology and occurrence/extent of sensory and trophic changes in the referred area. Five groups of subjects were studied, with: symptomatic gallbladder calculosis (3-20 colics); asymptomatic calculosis; symptomatic gallbladder shape abnormality (8-18 colics); asymptomatic shape abnormality; normal gallbladder/no symptoms. At the cystic point (CP) and contralaterally, all underwent measurement of: pain thresholds to electrical stimulation of skin, subcutis and muscle; thickness of subcutis and muscle via ultrasounds. ⋯ Patients with symptomatic calculosis were re-evaluated after 6 months; those not presenting further colics showed a significant increase in subcutis and muscle thresholds at CP, while those who continued presenting colics showed a further significant threshold decrease (0.01
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Comparative Study
Excitatory and modulatory effects of inflammatory cytokines and neurotrophins on mechanosensitive group IV muscle afferents in the rat.
In inflamed tissue--including skeletal muscle--the concentrations of cytokines and neurotrophins are known to increase. However, nothing is known about a possible contribution of these agents to muscle pain and hyperalgesia. The present study investigated acute effects of cytokines and neurotrophins on response properties of slowly conducting muscle afferents. ⋯ TNF-alpha and BDNF did not excite group IV units but had a desensitising action: after TNF-alpha or BDNF, the response magnitudes to pressure stimuli decreased significantly. The data indicate that cytokines and neurotrophins influence the impulse activity and mechanosensitivity of group IV muscle afferent units. These effects could be of functional significance when the agents are released from muscle cells under pathophysiological circumstances.