Pain
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Given the inherent variability in pain responding, using an "average" pain score may pose serious threats to internal and external validity. Using growth mixture modeling (GMM), this article first examines whether infants can be differentiated into stable groups based on their pain response patterns over a 2-minute post-needle period. Secondary analyses, to specifically address the issue of averaging pain scores to represent a sample, qualitatively described clinically meaningful differences between pain scores of the discerned groups and the overall mean (irrespective of groups). ⋯ Our secondary suggested that the overall mean pain score immediately post-needle reflected most groups well at every age. However, for older infants (6 and 12months, especially), the overall mean pain responses at 1 and 2minutes post-needle significantly over or underestimated groups that contained 48% to 100% of the sample. These results combined highlight the significant variability of infant pain responding patterns between groups of infants and furthermore, calls into question the validity of using an overall mean in research with older infants during the regulatory phase post-needle.
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The objective of this study was to examine the prevalence and patterns associated with past-year medical use, medical misuse, and nonmedical use of prescription opioids (NMUPO) among adolescents over a 2-year time period and to examine substance abuse, sleeping problems, and physical pain symptoms associated with these patterns of medical use, medical misuse, and NMUPO. A Web-based survey was self-administered by a longitudinal sample of 2050 middle and high school students in 2009-2010 (Year 1) and again in 2010-2011 (Year 2). The study was set in 2 southeastern Michigan school districts. ⋯ Multiple logistic regression analyses indicated that the odds of a positive screen for substance abuse in Year 2 were greater for adolescents who reported medical misuse or NMUPO for non-pain-relief motives in Year 1 compared with those who did not use prescription opioids. The findings indicate an increased risk for substance abuse among adolescents who report medical misuse or NMUPO for non-pain-relief motives over time. The findings have important clinical implications for interventions to reduce medical misuse and NMUPO among adolescents.
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Randomized Controlled Trial
A randomized, double-blind, placebo-controlled trial of a chemokine receptor 2 (CCR2) antagonist in posttraumatic neuralgia.
We evaluated the analgesic efficacy, safety and tolerability of a novel chemokine receptor 2 (CCR2) antagonist, AZD2423, in posttraumatic neuralgia. This was a double-blind, randomized, parallel-group, multicentre study. One hundred thirty-three patients with posttraumatic neuralgia were equally randomized to 28days' oral administration of 20mg AZD2423, 150mg AZD2423 or placebo. ⋯ The CCR2 antagonist AZD2423 demonstrated no efficacy on NRS average pain scores and most of the secondary pain variables. The NPSI data suggested possible effects on certain sensory components of pain. There were no major safety or tolerability concerns.
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Comparative Study
Noxious stimulation excites serotonergic neurons: a comparison between the lateral paragigantocellular reticular and the raphe magnus nuclei.
The present study was designed to record electrophysiological responses to graded noxious thermal stimuli of serotonergic and nonserotonergic neurons in the lateral paragigantocellular reticular (LPGi) and the raphe magnus (RMg) nuclei in rats. All of the neurons recorded were juxtacellularly filled with neurobiotin and identified with double immunofluorescent labeling for both neurobiotin and serotonin. Under halothane anesthesia (0.75%), noxious thermal stimuli ⩾48°C activated almost all (88%) of the serotonergic neurons located within the LPGi (n=16). ⋯ Recording of serotonergic neurons in the RMg (n=21) demonstrated that the proportion of strongly activated (>2spike/s) neurons (19% vs 59% for the LPGi) as well as the magnitude of the activation (2.1±0.4spike/s: mean of responses above the population median) to thermal noxious stimuli were significantly lower than in the LPGi (P<.05). Within the boundaries of both the LPGi and the RMg (B3 group), nonserotonergic neurons were also predominantly excited (75%) by noxious stimuli, and the resulting activation (7.9±1.2spike/s) was even greater than that of serotonergic neurons. Thermal noxious stimuli-induced activation of LPGi serotonergic cells probably plays a key role in serotonin-mediated modulations of cardiac baroreflex and transmission of nociceptive messages occurring under such intense noxious conditions.
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Factors underlying individual differences in pain responding are incompletely understood, but are likely to include genetic influences on basal pain sensitivity in addition to demographic characteristics such as age, sex, and ethnicity, and psychological factors including personality. This study sought to explore the relationship between personality traits and experimental pain sensitivity, and to determine to what extent the covariances between these phenotypes are mediated by common genetic and environmental factors. A sample composed of 188 twins, aged 23 to 35years, was included in the study. ⋯ In contrast, associations between HPI and personality seemed weak and unstable, but a significant effect of Angry Hostility (a facet of Neuroticism) emerged in generalized estimating equations analysis. Although the genetic correlation between these phenotypes was essentially zero, a weak but significant individual-specific environmental correlation emerged (re=.21, P<.05). Taken together, these findings suggest that CPI is more consistently related to personality dispositions than HPI, both phenotypically and genetically.