European journal of pain : EJP
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TRPA1 is a Ca-permeable nonselective cation channel expressed in sensory neurons and acts as a nocisensor. Recent reports show that some monoterpenes, a group of naturally occurring organic compounds, modulate TRP channel activity. Here, we report that limonene, being contained in citrus fruits and mushrooms, shows a unique bimodal action on TRPA1 channel. ⋯ Topically applied limonene stimulates TRPA1, resulting in elicitation of acute pain, but its systemic application inhibits nociception induced by oxidative stress. Because limonene is a safe compound, it may be utilized for pain control due to its inhibition of TRPA1 channels. What does this study add: Limonene, a monoterpene in essential oils of various plants, has been known for its antitumor and anti-inflammatory properties. However, molecular basis of their actions has not been identified. This study shows that limonene activates nociceptive TRPA1 and elicits acute pain, when it is topically applied. In addition, systemic application of limonene exerts inhibitory effects on nociception induced by an oxidative stress-induced TRPA1 activation.
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Chronic pain and fatigue are both common complaints in childhood and adolescence and often persist over time. The aim of the study was to investigate whether chronic pain/fatigue persists during adulthood and how former patients function and participate in society as adults. ⋯ A considerable number of these young adults still have pain/fatigue complaints in adulthood. More pain/fatigue pre-treatment during adolescence predict impaired functioning in the work-educational domain in young adulthood. WHAT DOES THIS STUDY ADD?: This study examines the social participation of young adults who suffered from severe chronic pain/fatigue during adolescence. Predictors for social participation are reported, as are the differences between young adults with and without persistent pain/fatigue complaints.
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Endometriosis is a common cause of pain including radicular pain. Ectopic endometrial tissue may directly affect peripheral nerves including the sciatic, which has not been modelled in animals. ⋯ Some especially painful forms of endometriosis are essentially neuropathic, because peripheral nerves are directly affected by nearby ectopic endometrial tissue. We modelled endometriosis by implanting autologous uterine tissue around rat sciatic nerve. We observed mechanical and cold pain behaviours along with signs of inflammation and nerve damage and increased pro-inflammatory cytokines at the implant site. Pain behaviours correlated with signs of nerve inflammation and damage rather than with cyst survival.
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Widespread musculoskeletal pain (WSP) and obesity frequently co-occur and may have shared risk factors. We aimed to investigate whether four dichotomized risk factors individually or jointly increase the risk for the onset of WSP and onset of obesity. ⋯ The onset of WSP and the onset of obesity were results of joint effects of exposures. Poor physical fitness was a key covariate in increasing the risk for both conditions. WHAT DOES THIS STUDY ADD?: In a general population, the new onset of widespread pain and new onset of obesity were results of joint effects of risk factors and particularly poor physical fitness. The study may aid in the identification of patients at risk of future disability.
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Numerous studies have found appraisals of pain as a source of potential threat or tissue damage influence pain perception and coping. Conversely, causal effects of challenge appraisals reflecting potential future benefits of bearing pain have received little attention. This experiment was designed to elucidate effects of appraising laboratory pain as a source of potential threat and challenge on pain perception and coping. ⋯ Findings underscore causal effects of pain appraisals on coping responses and pain perception. WHAT DOES THIS STUDY ADD?: Effects of challenge appraisals of pain as a source of potential future growth or development have not been considered in experimental pain research. Causal effects of primary appraisals of laboratory pain as a source of potential threat and challenge were elucidated in relation to pain perception and coping.