European journal of pain : EJP
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To elucidate neurophysiological mechanisms of persistent pain induced by tissue injury, the present study was designed to investigate the effects of s.c. bee venom injection on responses of the dorsal horn nociceptive neurons and those of behavior in anesthetized and awake cats, respectively. A parallel comparative study was also performed to compare the effects of s.c. bee venom and formalin injections on neuronal responses by using an extracellular single-unit recording technique. The present results showed that s.c. bee venom injection into the peripheral cutaneous receptive field resulted in a protracted, tonic monophase of increase in spike responses of wide-dynamic-range (WDR) neurons for more than 1 h, while injection of the same volume of vehicle did not have such an effect. ⋯ Comparative studies showed that the duration and frequency of the bee venom-induced neuronal responses were comparable to those induced by s.c. formalin; however, responses of WDR neurons to mechanical stimuli applied to the injection site of the two chemical agents were quite different. Bee venom produced a significant enhancement of mechanical responses of WDR neurons, while, on the contrary, formalin produced a desensitization of sensory receptors in the injection site, suggesting that the two tonic pain models may have different underlying mechanisms. Copyright 1998 European Federation of Chapters of the International Association for the Study of Pain.
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Positron emission tomography (PET) and accumulation of H(2)(15)O as a marker of neuronal activity were used to create maps of cerebral blood-flow changes evoked by painful heat stimulation in 10 subjects. Two levels of painful tonic and phasic heat stimuli were applied with use of a newly developed contact heat thermode on the volar surface of the dominant (right) arm. The subjects participated in two separate PET sessions. ⋯ Finally, the location of the activation site in the cingulate cortex was different from that observed during tonic heat pain. This study has provided more evidence for the existence of a common pain-processing network engaged during the perception of different levels of toxic and phasic heat pain. Copyright 1998 European Federation of Chapters of the International Association for the Study of Pain.
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Randomized Controlled Trial Clinical Trial
Multidisciplinary rehabilitation for chronic back pain in an outpatient setting: a controlled randomized trial.
Based on existing models for pain chronicity and effective treatment strategies for patients with chronic low back pain, a multidisciplinary rehabilitation programme for an outpatient group setting was developed. The main treatment components address the patient's physical functional capacity (functional restoring), cognitive and affective processes (pain management strategies), and behavioural and ergonomical aspects (back school elements). Short-term (immediately after intervention) and long-term effects (at 6-months follow-up) of the intervention were assessed in a randomized controlled study. ⋯ In contrast to post-treatment results, there were also significant improvements in strength and endurance. Overall results testify to the effectiveness of the intervention programme. Future studies (with larger sample sizes) should aim at a further improvement of functional capacity and disability perception, an analysis of differential treatment effects, and strategies for an improved long-term maintenance of the changes induced by the programme.
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Patients with complex regional pain syndrome (CRPS) (n=20) were examined in order to evaluate cutaneous reactions to norepinephrine (NE) on both the affected and the unaffected limb in comparison to healthy controls. Sixteen female and four male patients suffering from very acute and therefore untreated CRPS with a mean duration of 5.5 weeks were included in this study. Two groups of healthy volunteers served as control groups: the first group (n=18) according to the same study protocol as CRPS patients, and the second group (n=10) after warming up one limb. ⋯ The second control group had an increased unilateral skin temperature after warming up (35.0 vs 34.3 degrees C, p<0.006) and demonstrated a significantly increased vasoconstriction on the warmer side (52.0 vs 20.2%, p<0.03) corresponding to findings in patients with acute CRPS. The present study proves that there are signs of decreased sympathetic activity in the affected limb in very acute CRPS. However, no indication was found for increased sensitivity of vascular alpha-receptors in the very acute stages of CRPS, and there was also no indication for a significant direct contribution of the sympathetic nervous system to pain in very acute CRPS.