Pain
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Being physically active is often suggested to be important in the prevention and management of low back pain. This simple view does not take into account that the relation between the level of activity and back pain may be a U-shaped curve - i.e. both inactivity and excessive activities (back-unhealthy activity) present an increased risk for back pain. We explored the U-shaped association between physical activity and chronic low back pain (3 months duration) by analyzing cross-sectional data from the Dutch population-based Musculoskeletal Complaints and Consequences Cohort study (DMC(3), 1998) of a sex-age stratified sample of 25 years and older (n=3364). ⋯ A moderate increased risk for CLBP was found for both participants with a sedentary lifestyle (OR 1.31: 95% CI 1.08-1.58) and for those being involved in physical strenuous activities (OR 1.22: 95% CI 1.00-1.49). This was especially true for women (sedentary: OR 1.44: 95% CI 1.10-1.83; physically active: OR 1.36: 95% CI 1.04-1.78). This study provides some evidence that the relation between physical activity and CLBP is U-shaped.
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Sensory neuron-specific receptors (SNSRs) belong to a large family of GPCRs, known as Mrgs (Mas-related genes), many of which are preferentially expressed in primary afferent nociceptors. Selective SNSR agonists produce pain-like behaviors in rats, showing that SNSR activation is sufficient to produce pain. However, it is unknown whether SNSR activation is necessary for pain either in the normal condition or in pathological pain states. ⋯ In contrast, a selective TRPV1 antagonist abolished heat hyperalgesia produced by an SNSR agonist, suggesting that TRPV1 receptors mediate rSNSR1-evoked responses. We also found that rSNSR1-like immunoreactivity, like TRPV1, is localized in the superficial dorsal horn of the spinal cord. We propose that rSNSR1 represents a new member of the receptors expressed on chemosensitive nociceptors responsible for detecting the "inflammatory soup" of mediators generated by tissue damage.