Pain
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The present study was undertaken to examine the involvement of descending pain modulatory systems from the brainstem rostral ventromedial medulla (RVM) in modulating visceral hyperalgesia produced by intracolonic instillation of zymosan. Three hours after intracolonic zymosan, the visceromotor response (VMR) to noxious colorectal distension (CRD, 80 mmHg, 20s) was increased significantly. This hyperalgesia was attenuated in a dose-dependent manner by the selective NMDA receptor antagonist APV (10-30 fmol, 1 microl) microinjected into the RVM. ⋯ In contrast to the effects of APV and L-NAME, administration of the non-NMDA receptor antagonist DNQX into the RVM further enhanced the already facilitated VMR to CRD in zymosan-treated rats. Taken together, these data suggest that zymosan-produced visceral hyperalgesia is influenced by two descending pain modulatory systems: a facilitatory system mediated by activation of NMDA receptors in the RVM and production of nitric oxide, and an inhibitory system mediated by activity at non-NMDA receptors in the RVM. The unmasking of one system by selective blockade of the other suggests simultaneous activation of both by colonic inflammation.
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While attitudes toward pain have been identified as important mediators of patient adjustment to pain and response to treatment, research to date has focused on single attitude scales. The present study examined relations between attitude profiles and a set of variables reflecting clinical status in 395 chronic pain patients seen through a comprehensive pain center. A clustering procedure identified four distinct patient clusters, two of which displayed self-reliant attitude sets and two of which displayed medically oriented attitudes. ⋯ The medically oriented groups differed in terms of level of distress, with the more distressed group reporting pain of a greater duration. The results suggest that patients can be classified into attitudes profiles that are associated with meaningful differences in clinical status. Further research should investigate attitudes among more functional patients with chronic pain, especially as they affect the evolution of chronic pain syndromes.
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The present study examined the role of catastrophizing in predicting levels of pain and disability in a sample of individuals who had sustained soft-tissue injuries to the neck, shoulders or back following work or motor vehicle accidents. Participants were 86 (27 men, 59 women) consecutive referrals to the Atlantic Pain Clinic, a multidisciplinary treatment centre for the management of persistent pain disorders. Findings revealed that catastrophizing, measured by the Pain Catastrophizing Scale (PCS; Sullivan, M. ⋯ In addition, catastrophizing was associated with disability independent of the levels of depression and anxiety. The rumination subscale of the PCS was the strongest predictor of pain and disability. Theoretical and clinical implications of the findings are discussed.
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The mechanisms by which nerve growth factor (NGF) induces thermal hyperalgesia and neutrophil accumulation have been investigated in the rat. Thermal nociceptive thresholds in rat hind paw were measured as the time taken for paw withdrawal from a heat source and neutrophil accumulation was measured in hind paw and dorsal skin samples using a myeloperoxidase assay. NGF (23-80 pmol intraplantar (i.pl.) injection) induced a significant (P < 0.05, n = 6-16) thermal hyperalgesia at 5 h after injection and significant neutrophil accumulation (P < 0.05, n = 6) was observed with NGF (40 pmol). ⋯ The 5-lipoxygenase inhibitor ZM230487 (10 nmol co-injected with NGF) significantly attenuated neutrophil accumulation and hyperalgesia induced by NGF; unlike the histamine and 5-hydroxytryptamine antagonists (mepyramine and methysergide) which were without effect at the times measured. Furthermore, depletion of circulating neutrophils (using a rabbit anti-rat neutrophil antibody) abolished NGF induced hyperalgesia. These results indicate that neutrophils, which accumulate in response to a 5-lipoxygenase product, play a crucial role in NGF-induced hyperalgesia.
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Abnormal return of cutaneous sensibility is common after burn injuries and many patients complain of painful and/or paresthetic sensations in their healed wounds. However, little is known about the exact nature and severity of these problems. The present study was designed to provide a quantitative evaluation of the cutaneous sensibility in burned patients. ⋯ When symptomatic and asymptomatic sites were compared, significant deficits were observed in the tactile modality (touch-pressure). Other significant predictors of chronic sensory problems were burn depth and patients' age. Pathophysiological mechanisms of diminished sensibility in burned and unburned skin as long as several years after the injury are discussed along with those implicated in pain and paresthesia problems reported by the patients.