Pain
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Musculoskeletal pain is one of the most frequent symptoms for which medical assistance is sought. Yet, the majority of our knowledge regarding pain physiology is based on studies of cutaneous tissue. Comparatively little is known about activation of visceral, joint and perhaps least of all, musculoskeletal nociceptors although clinically-treated pain originates principally in these structures. ⋯ This behavioral dependent measure is also significantly reversed by agents used clinically to treat muscle pain, indomethacin and dexamethasone, as well as the non-competitive N-methyl-D-aspartate receptor antagonist MK801. Finally, evidence that reduction in grip force is in part mediated by small, unmyelinated afferents is provided by the demonstration that neonatal capsaicin treatment significantly reduced carrageenan-evoked behavioral hyperalgesia ( approximately 45% reduction) and reduced muscle content of immunoreactive CGRP ( approximately 60% reduction) relative to control levels. Collectively, these findings provide converging lines of evidence for the validity of this animal model to investigate mechanisms involved in the development of muscle hyperalgesia.
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We examined the relation between ectopic afferent firing and tactile allodynia in the Chung model of neuropathic pain. Transection of the L5 spinal nerve in rats triggered a sharp, four- to six-fold increase in the spontaneous ectopic discharge recorded in vivo in sensory axons in the ipsilateral L5 dorsal root (DR). The increase, which was not yet apparent 16 h postoperatively, was complete by 24 h. ⋯ Axotomy triggers a wide variety of changes in the neurochemistry and physiology of primary afferent neurons. Investigators studying DRG neurons in culture need to be alert to the rapidity with which axotomy, an inevitable consequence of DRG excision and dissociation, alters key properties of these neurons. Our identification of a specific population of neurons whose firing properties change suddenly and synchronously following axotomy, and whose activity is associated with tactile allodynia, provides a powerful vehicle for defining the specific cascade of cellular and molecular events that underlie neuropathic pain.
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This study outlines the design and validation of a new self-administered instrument for assessing foot pain and disability. The 19-item questionnaire was tested on 45 rheumatology patients, 33 patients who had attended their general practitioner with a foot-related problem and 1000 responders to a population survey of foot disorders. Levels of reported disability were found to be greatest for rheumatology patients and least for community subjects. ⋯ A Cronbach's alpha value of 0.99 and item-total correlation values between 0.25 and 0.62 confirmed the internal consistency of the instrument. Finally the results of a principal components analysis identified three constructs that reflected disabilities that are associated with foot pain: functional limitation, pain intensity and personal appearance. The design of the foot disability questionnaire makes it a suitable instrument for assessing the impact of painful foot conditions in both community and clinical populations.
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Randomized Controlled Trial Comparative Study Clinical Trial
The cognitive and psychomotor effects of morphine in healthy subjects: a randomized controlled trial of repeated (four) oral doses of dextropropoxyphene, morphine, lorazepam and placebo.
Ten healthy subjects (four male) of mean age 31 years (range 25-40) took part in a randomized double-blind four-way crossover study to examine the cognitive and psychomotor effects of repeated oral doses of dextropropoxyphene and morphine. Four treatments were compared: dextropropoxyphene napsylate 100 mg, morphine sulphate 10 mg, lorazepam 0.5 mg and placebo. Four doses of each drug were given at 4-h intervals to each subject on four separate study days at least 1 week apart. ⋯ Dextropropoxyphene impaired performance on choice reaction time and picture recognition. These data show that oral morphine may enhance performance in some measures of cognitive function, whereas dextropropoxyphene (in usual therapeutic doses) seems more likely to cause impairment. Neither opioid has substantial effects on cognition and psychomotor function compared with lorazepam.
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Randomized Controlled Trial Comparative Study Clinical Trial
Pain and allodynia/hyperalgesia induced by intramuscular injection of serotonin in patients with fibromyalgia and healthy individuals.
The aim of this study was to investigate the effect of injection of serotonin (5-HT) into the masseter muscle on pain and allodynia/hyperalgesia. Twelve female patients with fibromyalgia (FM) and 12 age-matched female healthy individuals (HI) participated in the study. The current pain intensity (CPI) and the pressure pain threshold (PPT) of the superficial masseter muscles were assessed bilaterally. 5-HT in one of three randomized concentrations (10(-3), 10(-5), 10(-7) M) or isotonic saline was then injected into either of the two masseter muscles in a double-blind manner. ⋯ In the HI-group pain developed significantly after injection irrespective of whether 5-HT or saline was injected, but significantly more so after 5-HT at 10(-3) M than saline injection. CPI decreased quickly and then remained on a very low level for most of the experiment. 5-HT at both 10(-5) M and 10(-3) M caused a significantly greater decrease of PPT than saline. In conclusion, our results show that 5-HT injected into the masseter muscle of healthy female subjects elicits pain and allodynia/hyperalgesia, while no such responses occur in patients with fibromyalgia.