Articles: hyperalgesia.
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Randomized Controlled Trial
Local pain and spreading hyperalgesia induced by intramuscular injection of nerve growth factor are not reduced by local anesthesia of the muscle.
Injections with local anesthesia for therapeutic and diagnostic purposes are common clinical practice. This double-blind placebo controlled study explores the rational of local anesthetic blocks for the detection of muscle pain as the primary generator in spreading hyperalgesic conditions. ⋯ Muscle pain and spreading hyperalgesia induced by NGF is maintained despite anesthesia of the primary nociceptive locus. This indicates that intramuscular injection of local anesthetics may not be a valid diagnostic method for primary muscle pain.
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Motor cortex stimulation (MCS) has been used to treat patients with neuropathic pain resistant to other therapeutic approaches; however, the mechanisms of pain control by MCS are still not clearly understood. We have demonstrated that MCS increases the nociceptive threshold of naive conscious rats, with opioid participation. In the present study, the effect of transdural MCS on neuropathic pain in rats subjected to chronic constriction injury of the sciatic nerve was investigated. ⋯ Zif268 results were similar to those obtained for Fos, although no changes were observed for Zif268 in the anterior cingulate cortex and the central amygdaloid nucleus after MCS. The present findings suggest that MCS reverts neuropathic pain phenomena in rats, mimicking the effect observed in humans, through activation of the limbic and descending pain inhibitory systems. Further investigation of the mechanisms involved in this effect may contribute to the improvement of the clinical treatment of persistent pain.
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Evidence of support for sensory changes during minor depression and sadness is scarce and the neural mechanisms are unclear. We assessed central pain processing engaged in nociceptive C-fiber polymodal activity by examining the perception of a non-noxious unpleasant burning sensation induced by a thermal grill illusion, in 26 nonpatients with minor depression (19 females) and 28 healthy subjects (18 females), between 19 and 61 years old and pain free at the study. Controls were also subjected to induction of transient moods. Subjects with depression reported increased pain perception; this increase was more pronounced for the affective dimension of pain (unpleasantness) than for its sensory dimension (intensity). The perception of pain unpleasantness, pain intensity, and overall pain showed positive and linear correlations with depression levels measured by Zung's and Beck's scales. In controls, sad mood induction only increased the scores assigned to negative mood-describing adjectives; the perception of pain intensity, unpleasantness, and overall pain were significantly increased following sad, but not neutral or elevated, mood inductions. Yet, pain intensity and unpleasantness were correlated linearly and reciprocally to positive, instead of negative, mood-describing adjective scores. Thus, there is a central thermal hyperalgesia in subjects with minor depression and sadness. ⋯ There is a central thermal hyperalgesia in subjects with minor depression, probably associated with an enhanced central processing of nociceptive C-fiber polymodal activity at anterior cingulate cortex, that is predominately expressed as an increased unpleasantness and that could be in part counteracted by behavioral therapies leading to mood elevation.