European journal of pain : EJP
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This study investigated attentional biases for linguistic pain-related stimuli in individuals suffering from chronic headaches and healthy controls. Attentional bias was assessed using a visual probe (also reported as dot probe in previous investigations) task which presented pain-related (sensory and affective) and neutral words at two exposure duration conditions, 500 and 1250 ms. ⋯ No significant differences between groups were found in attentional bias scores at the shorter stimulus duration of 500 ms, which instead correlated significantly with trait anxiety. Results are discussed in relation to research into pain-related and anxiety-related biases in initial orienting and maintained attention.
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There is increasing evidence that spinal glial cells play an important role in chronic pain states. However, so far no data on the role of microglia in muscle pain are available. The aim of the present study was to investigate the involvement of spinal microglial cells in chronic muscle pain. ⋯ This indicates that microglial cells were activated by the myositis and withdrew their processes. Chronic intrathecal administration of minocycline or anti TNF-alpha with an osmotic mini-pump largely normalised the inflammation-induced changes in spontaneous exploratory behaviour and attenuated the hypersensitivity to mechanical stimulation. Both the immunohistochemical and behavioural data show that spinal microglial cells are involved in nociceptive processes in the cause of a chronic muscle inflammation.
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Nitric oxide, which has been implicated in the development of hyperalgesia in the spinal system, has not been systematically studied in the trigeminal system, especially in the context of inflammatory muscle pain condition. In this study, we investigated the functional role of centrally released nitric oxide in the pathogenesis of orofacial muscle pain. Specifically, we examined the contribution of neuronal, inducible and endothelial nitric oxide synthases, nNOS, iNOS and eNOS, respectively, in mediating masseter hypersensitivity under acute inflammatory condition. ⋯ The expression of all three nitric oxide synthases was significantly up-regulated 30-60 min following capsaicin stimulation, which paralleled the time course of the development of capsaicin-induced masseter hypersensitivity. Pretreatment with each NOS inhibitor significantly attenuated the masseter hypersensitivity. These data showed that all three NOS in the Vc are functionally important for the development of craniofacial muscle hyperalgesia and suggest that the three NOS are closely orchestrated to regulate the level of nitric oxide under normal and pathologic conditions.