Pain
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Cannabinoids act at receptors on peripheral and central neurons to modulate diverse physiological functions and produce analgesia. Corneal sensory nerves express the CB1 cannabinoid receptor and project to two spatially discrete regions of the lower brainstem, the trigeminal interpolaris/caudalis (Vi/Vc) transition and subnucleus caudalis/upper cervical cord (Vc/C1) junction region. The function of CB1 expression on corneal nerves is not known. ⋯ These results indicated that cannabinoid receptor agonists acted, at least in part, at CB1 receptors in the anterior eye to reduce corneal stimulation-evoked trigeminal brainstem neural activity. Corneal nociceptor-evoked activity at the Vi/Vc transition was reduced significantly by topical WIN-2, while activity at the Vc/C1 junction region displayed only minor decreases. These findings were consistent with the hypothesis that CB1 receptors affect the activity of corneal-responsive neurons that preferentially contribute to homeostasis of the anterior eye and/or reflexive aspects of nociception rather than the sensory-discriminative aspects of corneal nociception.
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Meta Analysis Comparative Study
A comparison of placebo effects in clinical analgesic trials versus studies of placebo analgesia.
A previous meta-analysis of clinical analgesic trial studies showed generally low magnitudes of placebo analgesia (N. Engl. J. ⋯ This difference as well as differences in effect sizes within studies of placebo mechanisms may be parsimoniously explained by differences in expected pain levels produced by placebo suggestions and by conditioning. Furthermore, some of the studies of placebo analgesic mechanisms indicate that the magnitude of placebo analgesia is higher when the placebo analgesic effect is induced via suggestion combined with conditioning than via suggestion alone or conditioning alone. Based on these findings, we suggest that placebo analgesic effects are most optimally conceptualized in terms of perception of the placebo agent, and therefore a new definition of placebo response is proposed.
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This study investigated dimensions of chronic pain and temporomandibular disorders (TMDs) in a census tract sampling of African-American and Caucasian young women enrolled (from racially congruent households) at ages 9-10 in the longitudinal multicenter National Heart Lung and Blood Institute's Growth and Health Study (NGHS). The present study, which examined participants at the California clinical NGHS center when they were 19-23 years old, investigates five commonly reported chronic pains: back, head, face/jaw, abdomen, and chest. Chronic pain grade (CPG) status based on pain self-reports (frequency, duration, severity, and interference with usual activities) is reported for each of the five pain sites. ⋯ Racial differences were not found for back, head, abdomen or chest pains. However, significant racial differences were found regarding facial pain and symptoms related to TMDs above and beyond socioeconomic status (SES) (lifetime prevalence: adjusted odds ratio (aOR)=2.14 and 95% confidence interval (CI)=1.40-3.31; 6 month period prevalence: aOR=2.03 and 95% CI=1.16-3.64). Not only were facial pain and jaw symptoms reported more frequently by Caucasians compared to African-Americans controlling for SES, but they were also reported to have an earlier onset.
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Fear-avoidance beliefs and catastrophizing have been shown to be powerful cognitions in the process of developing chronic pain problems and there is a need for increased knowledge in early stages of pain. The objectives of this study were therefore, firstly, to examine the occurrence of fear-avoidance beliefs and catastrophizing in groups with different degrees of non-chronic spinal pain in a general population, and secondly to assess if fear-avoidance beliefs and catastrophizing were related to current ratings of pain and activities of daily living (ADL). The study was a part of a population based back pain project and the study sample consisted of 917 men and women, 35-45 years old, either pain-free or with non-chronic spinal pain. ⋯ The study showed two relationships, which were between fear-avoidance and ADL as well as between catastrophizing and pain intensity. Logistic regression analyses were performed with 95% confidence intervals and the odds ratio for fear-avoidance beliefs and ADL was 2.5 and for catastrophizing and pain 1.8, both with confidence interval above unity. The results suggest that fear-avoidance beliefs and catastrophizing may play an active part in the transition from acute to chronic pain and clinical implications include screening and early intervention.
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Comparative Study
Patient-related barriers to pain management: the Barriers Questionnaire II (BQ-II).
Patients' beliefs can act as barriers to optimal management of cancer pain. The Barriers Questionnaire (BQ) is a tool used to evaluate such barriers. Here, the BQ has been revised to reflect changes in pain management practices, resulting in the Barriers Questionnaire-II (BQ-II), a 27-item, self report instrument. ⋯ BQ-II scores were related to measures of pain intensity and duration, mood, and QOL. Patients who used adequate analgesics for their levels of pain had lower scores on the BQ-II than did patients who used inadequate analgesics. The BQ-II is a reliable and valid measure of patient-related barriers to cancer pain management.