Pain
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Comparative Study
The development and preliminary validation of a brief measure of chronic pain impact for use in the general population.
From a biopsychosocial perspective, assessing chronic pain's psychological impact should involve at minimum the measurement of pain severity, functional interference, and pain-related emotional burden. This article details the development of a brief instrument, the 15-item Profile of Chronic Pain: Screen (PCP:S), designed to address these three key elements in a national (US) sample of over 2400 individuals recruited via random digit dialing. Retest reliability, internal consistency, and preliminary validity were excellent. ⋯ A series of confirmatory factor analyses on several distinct samples revealed a stable, 3-factor solution reflecting pain severity, interference, and emotional burden. Finally, national norms were developed by gender and three age groups. In view of its strong psychometric properties, the PCP:S has the potential to serve as a brief, cost-effective assessment tool for identifying individuals whose chronic pain merits more detailed psychosocial evaluation.
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Comparative Study Clinical Trial
Gender differences in pain modulation evoked by repeated injections of glutamate into the human trapezius muscle.
Gender differences in pain habituation, temporal summation, and pressure hyperalgesia evoked by repeated injections of glutamate into the dominant trapezius muscle were investigated. The glutamate-evoked muscle pain intensity and pressure pain threshold (PPT) were assessed. The PPTs were measured bilaterally in the trapezius muscles (local pain area) and posterolateral neck muscles (referred pain area) after glutamate injection in healthy and age-matched males and females (each n=14). ⋯ No PPTs changes were observed either in the contralateral trapezius muscle or bilaterally in the referred pain areas in either sex. These results suggest that a less efficient pain habituation and a greater susceptibility to the development of temporal summation of muscle pain in females, but not in males, might be one of the contributing factors to the higher incidence of neck shoulder pain in females. In addition, the reduction of PPTs in the local pain area evoked by intramuscular glutamate injection may represent an early process of peripheral pressure hyperalgesia, which is most likely gender independent.
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Comparative Study
Parent-child interactions among children with juvenile fibromyalgia, arthritis, and healthy controls.
Parent-child interactions during pain-inducing exercise tasks among children (11-17 years old) with fibromyalgia, juvenile rheumatoid arthritis, and pain-free controls were examined and the contribution of parent-child interactions to disability was tested. Fifteen children in each of the three diagnostic groups and their parents completed 5-min exercise tasks and completed questionnaire measures of disability (Functional Disability Inventory) and coping (Pain Coping Questionnaire). There were few group differences in parent-child interactions. ⋯ Across the groups, more pain and less time on task during the exercises were related to Functional Disability Inventory scores and more school absences. Parent-child interaction patterns influence children's adaptation to pain during experimental tasks. Parents' discouragement of coping in response to their children's negative statements related to the pain or the pain-evoking task are counter productive to children's ability to maintain activity in a mildly painful situation.
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Tumor necrosis factor alpha (TNFalpha) and interleukin 1beta (IL-1beta) are pro-inflammatory cytokines capable of altering the sensitivity of sensory neurons. Because sensitization elicited by IL-1beta and TNFalpha is blocked by inhibition of the inducible enzyme, cyclooxygenase-II (COX-2), we examined whether these cytokines could increase COX-2 expression in dorsal root ganglion (DRG) cultures. Treatment of cell cultures with either IL-1beta or TNFalpha increases immunoreactive COX-2, as measured by immunoblotting, in a time- and concentration-dependent manner. ⋯ IL-1beta and TNFalpha treatment for 24 h enhanced prostaglandin E2 (PGE2) production 2-4-fold, which was blocked by pretreatment with the COX-2 inhibitor, NS-398. Exposing cultures to PGE2, IL-1beta, or TNFalpha for 24 h did not alter PGE2 receptor (EP) mRNA levels. These results indicate that TNFalpha and IL-1beta induce the functional expression of COX-2 but not EP receptors in DRG cells in culture and suggest that cytokine-induced sensitization of sensory neurons is secondary to prostaglandin production and not alterations in EP receptors.
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Comparative Study
Differential susceptibility of the PAG and RVM to tolerance to the antinociceptive effect of morphine in the rat.
The periaqueductal gray (PAG) and rostral ventromedial medulla (RVM) are part of a nociceptive modulatory system. Microinjection of morphine into either structure produces antinociception. Tolerance develops to ventrolateral PAG mediated antinociception with repeated microinjection of morphine. ⋯ There was a 64% drop in hot plate latency from the first to the fifth injection of morphine into the PAG, but only a 36% drop in latency following RVM microinjections. Reducing the interdose interval to two injections a day or increasing the total number of injections from 4 to 8 did not enhance the development of tolerance to RVM morphine administration. These data demonstrate that opioid-sensitive neurons in the RVM are relatively resistant to the development of tolerance compared to PAG neurons.