The journal of pain : official journal of the American Pain Society
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Chronic-constriction injury (CCI) of the sciatic nerve causes mechanical and heat hyperalgesia and mechanical allodynia in the plantar surface of the hindpaw. The underlying mechanism thought to account for these phenomena include central sensitization induced by peripheral nerve injury, ie, the increase in neuronal activity of spinal dorsal horn neurons. As a marker of neuronal activation of the central nervous system, Fos expression has been used widely to monitor the change in neuronal activity evoked by peripheral input. ⋯ The number of noxious stimulus-evoked Fos-labeled neurons in both the superficial and deep laminae of the dorsal horn in the CCI rats was increased significantly compared with those in sham-operated rats, suggesting an increased excitability of dorsal horn neurons to noxious stimuli. Concurrent EA treatment to the Zusanli point with the pinch stimulus suppressed the increase in the number of Fos-labeled cells in the spinal dorsal horn in the CCI rats. The present results show that EA treatment has antinociceptive effects on both pain behavior and neuronal activation of the spinal dorsal horn neurons in CCI rats.
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According to the fear avoidance model, prolonged disability among patients with chronic nonmalignant pain is due, in part, to an exaggerated fear of pain. At issue in the present study was an attempt to refine the fear-avoidance hypothesis by eliciting estimates of anticipated pain as well as anticipated injury. Along with scores on the Fear Avoidance Beliefs Questionnaire-Work (FABQ-W), a validated measure of fear avoidance, pain and injury expectancies were used as predictors of work disability in a hierarchical regression model. ⋯ After controlling for pain duration, depression, somatization, and current pain severity, pain expectancy alone accounted for 16% of the variance in patients in the chronic group (P < .001) and 33% of the variance in patients in the acute group (P < .001). Both pain and injury expectancies were associated equally with work disability for patients in the acute group (P < .001), but only pain expectancy accounted for variance in the chronic group (P < .001). Fear-avoidance beliefs, in the form of cognitive expectancies, may have as much influence on the duration of disability in patients with acute pain as they do in patients with chronic pain.