Articles: pain-threshold.
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Psychophysical assessments of orofacial sensory function were performed in order to investigate neurophysiological aspects of the burning mouth syndrome (BMS). ⋯ The presence of abnormal prepain perceptions and disturbances in the perception of nonnociceptive and nociceptive thermal stimuli applied on both pain-affected and normal regions suggest a perceptual deficit unrelated to specific pathophysiological mechanisms in BMS. However, it appears that a psychological explanation of BMS should be used cautiously, as the present results suggest alterations in sensory function.
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1. Peripheral nerve injury sometimes leads to the development of neuropathic pain. One of the symptoms of such neuropathic pain is mechanical allodynia, pain in response to normally innocuous mechanical stimuli. ⋯ The response characteristics of MRAs change to those of typical RAs after a systemic injection of phentolamine, an alpha-adrenergic receptor blocker. 5. We conclude that many RAs become abnormal under the influence of sympathetic efferents in neuropathic pain, so that their response patterns change to those of MRAs. We propose that this abnormality is responsible for signaling the mechanical allodynia that can be seen in neuropathic pain states such as causalgia.
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1. The aim of this study was to develop a quantitative behavioral model of nociception. Electromyographic (EMG) recordings from a hamstring flexor muscle provided a measure of the magnitude of hindlimb withdrawals elicited by brief, graded noxious contact thermal stimuli applied to the hindpaw in conscious rats. 2. ⋯ The decrement in withdrawal magnitude was greater at lower stimulus intensities and shorter interstimulus intervals, and transferred to a nearby (7.5 mm) but not distant (2.5 cm) site. Evidence for dishabituation was also obtained. 5. The advantages of this method as an animal model of nociception are presented and discussed in terms of the underlying neural circuitry and its modulation.
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1. To quantitatively investigate a nocifensive behavioral response, we developed a method to measure the magnitude of the rat's tail flick reflex and its modulation. A radial array of force transducers measured forces of tail flicks (in rostral, horizontal, and vertical planes) elicited by graded noxious radiant thermal stimulation of the conscious rat's tail, from which the overall movement vector was calculated. 2. ⋯ These observations are consistent with habituation of the tail flick reflex. 5. This method, therefore, provides a quantitative and reproducible measure of tail flick reflex magnitude that is sensitive to morphine. The underlying neural circuitry of the tail flick reflex is discussed in relation to limb withdrawal reflexes.