European journal of pain : EJP
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The formalin test is a well-established model for assessing nociceptive processes and analgesic drug effects. Previous studies have provided statistical validation of optimal procedures for conducting and scoring the rat formalin test. In the mouse model, formalin concentration has been subjected to validation studies. ⋯ Multiple regression analyses defined the optimal second-phase formalin response in outbred, Swiss-Webster mice as 15-35 min post formalin injection, and revealed that the second-phase response is best characterized by the cumulative time spent biting/licking the injected paw. Finally, paw physiological measures provided convergent evidence of nociceptive and antinociceptive processes in the mouse formalin test. Copyright 1998European Federation of Chapters of the International Association for the Study of Pain.
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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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Positive results of pilot studies of the effect of staphylococcus toxoid vaccine in patients with fibromyalgia and chronic fatigue syndrome were the incitement to the present, placebo-controlled study. It included 28 patients who fulfilled the criteria for both fibromyalgia and chronic fatigue syndrome. The effect of vaccination with a staphylococcus toxoid was compared with the effect of injections of sterile water. ⋯ Fifty percent were rehabilitated successfully and resumed half-time or full-time work. The results of this study support the authors>> hypothesis that treatment with staphylococcus toxoid may be a fruitful strategy in patients with fibromyalgia and chronic fatigue syndrome. 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.