Pain
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Comparative Study
Pain activation of human supraspinal opioid pathways as demonstrated by [11C]-carfentanil and positron emission tomography (PET).
The role of the supraspinal endogenous opioid system in pain processing has been investigated in this study using positron emission tomography imaging of [11C]-carfentanil, a synthetic, highly specific mu opioid receptor (mu-OR) agonist. Eight healthy volunteers were studied during a baseline imaging session and during a session in which subjects experienced pain induced by applying capsaicin topically to the dorsal aspect of the left hand. ⋯ This decrease varied directly with ratings of pain intensity. These results suggest that the supraspinal mu-opioid system is activated by acute pain and thus may play a substantial role in pain processing and modulation in pain syndromes.
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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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Plasticity in the spinal dorsal horn may underlie the development of chronic pain following peripheral nerve injury or inflammation. In this study, we examined whether chronic constriction injury of the sciatic nerve was associated with changes in the immunoreactive content of cyclic AMP response element binding protein (CREB), protein kinase A (PKA), and calcineurin Aalpha and Abeta in the spinal dorsal horn. In animals exhibiting thermal hyperalgesia as a behavioral sign of neuropathic pain 7 days after loose ligation of the sciatic nerve (chronic constriction injury), there was a significant increase in the content of phosphorylated (activated) CREB (pCREB). ⋯ In contrast, there were no differences in the content of non-phosphorylated CREB, and phosphorylated or non-phosphorylated PKA between control and sciatic ligation animals either 7 or 28 days after surgery. These data established a close association in the expression of thermal hyperalgesia with CREB activation and decreased calcineurin content in the spinal dorsal horn. The data revealed a significant but reversible shift in the manner in which spinal neurons processed sensory information following peripheral nerve injury, and lent further support to the notion that plasticity in the spinal dorsal horn may have contributed to the development of chronic pain.
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Features of somatisation have been shown to predict the onset of widespread body pain. This study aims to determine to what extent persons with orofacial pain syndromes share these features and to what extent they are uniquely related to oral mechanical factors. We have conducted a population-based cross-sectional survey in the South-East Cheshire area of the United Kingdom involving 2504 individuals aged 18-65 years. ⋯ Several oral mechanical factors were significantly associated with both orofacial pain and widespread body pain (grinding teeth, clicking jaw, missing teeth), while two (facial trauma, locking jaw) were specifically related to orofacial pain. Both pain syndromes were associated equally with high levels of psychological distress, indicators of somatisation and maladaptive response to illness. These results suggest that orofacial pain syndromes may commonly be a manifestation of the process of somatisation and the excess reporting of some local mechanical factors amongst persons with these symptoms, may not be uniquely associated with pain in the orofacial region.