Pain
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Clinical Trial
Do nerve growth factor-related mechanisms contribute to loss of cutaneous nociception in leprosy?
While sensory loss in leprosy skin is the consequence of invasion by M. leprae of Schwann cells related to unmyelinated fibres, early loss of cutaneous pain sensation, even in the presence of nerve fibres and inflammation, is a hallmark of leprosy, and requires explanation. In normal skin, nerve growth factor (NGF) is produced by basal keratinocytes, and acts via its high affinity receptor (trk A) on nociceptor nerve fibres to increase their sensitivity, particularly in inflammation. We have therefore studied NGF- and trk A-like immunoreactivity in affected skin and mirror-site clinically-unaffected skin from patients with leprosy, and compared these with non-leprosy, control skin, following quantitative sensory testing at each site. ⋯ Keratinocyte trk A expression (which mediates an autocrine role for NGF) was increased in clinically affected and unaffected skin, suggesting a compensatory mechanism secondary to reduced NGF secretion at both sites. We conclude that decreased NGF- and SNS/PN3-immunoreactivity, and loss of intra-epidermal innervation, may be found without sensory loss on quantitative testing in clinically-unaffected skin in leprosy; this appears to be a sub-clinical change, and may explain the lack of cutaneous pain with inflammation. Sensory loss occurred with reduced sub-epidermal nerve fibres in affected skin, but these still showed trk A-staining, suggesting NGF treatment may restore pain sensation.
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Clinical Trial
Do beliefs, coping, and catastrophizing independently predict functioning in patients with chronic pain?
Physical and psychosocial disability in patients with chronic pain have been shown to be associated with patients' pain-related beliefs, tendency to catastrophize, and pain coping strategy use. However, little is known about whether beliefs, catastrophizing, and coping strategies are independently associated with patient adjustment. Identification of specific beliefs, cognitive responses, and coping strategies strongly and independently associated with physical and psychosocial functioning would suggest the importance of targeting those variables for modification in treatment. ⋯ Belief scores significantly and independently predicted both physical disability and depression, after controlling for age, sex, pain intensity, catastrophizing, and coping. Coping scores significantly and independently predicted physical disability, but not depression, whereas catastrophizing independently predicted depression, but not physical disability. These findings suggest the importance of targeting specific pain-related beliefs and coping strategies, as well as catastrophizing, for modification in the treatment of patients with chronic pain.
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Much of our current understanding about chronic pain and the mechanisms of nociception has been derived from animal models (Bennett GJ. Animal models of neuropathic pain. In: Gebhart, GF, Hammond DL, Jensen TS, editors. ⋯ One such model that is frequently used in animals to study pain associated with inflammation is the subcutaneous injection of complete Freund's adjuvant (CFA). For ethical reasons, however, little information is available from humans concerning pain associated with this form of inflammation. Due to an inadvertent subcutaneous injection of CFA into the terminal phalanx of this investigator, a study with an N of 1, was conducted to compare the subjective effects of CFA-induced inflammation with objective measurements.
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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.