Articles: pain-threshold.
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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. 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.
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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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Randomized Controlled Trial Clinical Trial
Right-left asymmetry in tonic pain perception and its modification by simultaneous contralateral noxious stimulation.
Administration of the cold pressor test (I test) in normal healthy subjects revealed lateralization of pain perception with the right hand showing higher threshold and tolerance, as well as lower pain scores on Graphic Rating Scale, PPI and MPQ. To find out whether this lateralization persists, the cold pressor test was given while the contralateral hand was simultaneously exposed to non-noxious stimulus (II test) or noxious stimulus (III test). Reversal of laterality to the left hand was observed in the III test in 40% of the subjects for pain threshold. The mechanism of diffuse noxious controls and attentional focus to the noxious stimulus that is more intense, are suggested for the observed changes in laterality when two concurrent noxious stimuli are present.
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Pressure pain thresholds (PPT) of 39 normal subjects (20 males and 19 females) and 30 female patients with temporomandibular joint (TMJ) capsulitis (21 lateral and 25 posterior capsulitis) were examined by an electronic algometer. In normal subjects, statistically significant correlation coefficients were obtained from the values of intra-examiners and inter-examiners in both lateral and posterior TMJ capsules (p < 0.01). A comparison with data obtained from contralateral sides failed to demonstrate significant differences. Statistically significant differences were found between the PPT of normal female subjects and female patients with capsulitis in both lateral and posterior TMJ capsules (p < 0.01).