Pain
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Comparative Study
Temporal summation of pain from mechanical stimulation of muscle tissue in normal controls and subjects with fibromyalgia syndrome.
Individuals diagnosed with fibromyalgia syndrome (FMS) report chronic pain that is frequently worsened by physical activity and improved by rest. Palpation of muscle and tendinous structures suggests that nociceptors in deep tissues are abnormally sensitive in FMS, but methods of controlled mechanical stimulation of muscles are needed to better characterize the sensitivity of deep tissues. Accordingly, force-controlled mechanical stimulation was applied to the flexor digitorum muscle of the forearm in a series of brief contacts (15 stimuli, each of 1s duration, at 3 or 5s interstimulus intervals). ⋯ Furthermore, painful after-sensations were greater in amplitude and more prolonged for FMS subjects. These observations complement a previous demonstration that temporal summation of pain and after-sensations elicited by thermal stimulation of the skin are moderately enhanced for FMS subjects. Abnormal input from muscle nociceptors appears to underlie production of central sensitization in FMS that generalizes to input from cutaneous nociceptors.
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Randomized Controlled Trial Comparative Study Clinical Trial
Placebo analgesia and the heart.
Placebo-activated endogenous opioids act on pain mechanisms inducing analgesia, as well as on the respiratory centers inducing respiratory depression. Here, we show that placebo analgesia is accompanied by a reduced beta-adrenergic activity of the heart. We measured heart rate during placebo-induced expectation of analgesia, both in the clinical and the laboratory setting. ⋯ By contrast, both placebo responses were present during muscarinic blockade with atropine, indicating no involvement of the parasympathetic system. In order to better understand the effects of naloxone and propranolol, we performed a spectral analysis of the heart rate variability for the identification of the sympathetic and parasympathetic components, and found that the beta-adrenergic low frequency (0.15 Hz) spectral component was reduced during placebo analgesia, an effect that was reversed by naloxone. These findings indicate that placebo analgesia is accompanied by a complex cascade of events which affect the cardiovascular system.
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There has been a surge in interest in medicinal cannabis in Canada. We conducted a questionnaire survey to determine the current prevalence of medicinal cannabis use among patients with chronic non-cancer pain, to estimate the dose size and frequency of cannabis use, and to describe the main symptoms for which relief was being sought. Over a 6-week period in mid-2001, 209 chronic non-cancer pain patients were recruited in an anonymous cross-sectional survey. ⋯ We conclude that cannabis use is prevalent among the chronic non-cancer pain population, for a wide range of symptoms, with considerable variability in the amounts used. Discussions between patients and health care providers concerning cannabis use may facilitate education and follow up, and would allow side effects and potential interactions with other medications to be monitored. Clinical trials of cannabis for chronic non-cancer pain are warranted.
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Case Reports
Musculoskeletal pain in the Netherlands: prevalences, consequences and risk groups, the DMC(3)-study.
The objective of this paper was to present estimates on the prevalence of musculoskeletal pain of five different anatomical areas and ten anatomical sites, and their consequences and risk groups in the general Dutch population. Cross-sectional data from a population-based study of a sex-age stratified sample of Dutch inhabitants of 25 years and older were used. With a postal questionnaire data was assessed on musculoskeletal pain, additional pain characteristics (location, duration, course), its consequences (utilization of health care, sick leave and limitation in daily life) and general socio-demographic characteristics. ⋯ Between 33 and 42% of those with complaints consulted their general practitioner about their pain. With the exception of persons who are work disabled, general sociodemographic characteristics cannot be used to identify high risk groups. Musculoskeletal pain is common in all subgroups of the population and has far-reaching consequences for health, work and the use of health care.
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Comparative Study
Involvement of local cholecystokinin in the tolerance induced by morphine microinjections into the periaqueductal gray of rats.
The ventrolateral periaqueductal gray (PAG) is a key structure for the development of opioid tolerance. An increased activity of 'anti-opioids' like cholecystokinin (CCK) has been proposed as a possible mechanism for opioid tolerance. The present study evaluates the role of PAG-located CCK in the opioid tolerance induced by repeated microinjections of morphine (MOR) into PAG. ⋯ These results show that CCK has anti-opioid activity in PAG and that tolerance to MOR in PAG can be prevented or reversed if CCK receptors are blocked with PRO. Finally, opioid tolerance induced by repeated systemic MOR injections (5mg/kg intraperitoneal ) was reversed by a single microinjection of PRO into PAG. This emphasizes the central importance of PAG in the MOR/CCK interactions that lead to opioid tolerance.