Articles: pain-threshold.
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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).
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Sci. China, Ser. B, Chem. Life Sci. Earth Sci. · Jul 1993
Inhibitory effect of anisodamine on the neuropathic hyperalgesia following peripheral nerve injury (II).
A peripheral neuropathy with hyperalgesia and allodynia was produced by loosely tying constrictive ligature around the left sciatic nerve of rats, i.v. injection of anisodamine 20 mg/Kg abolished both neuropathic hyperalgesia responses to noxious radiant heat and ectopic discharges generated from the injured region of the nerve. Anisodanime applied either systemically or locally to the damaged area of the nerve not only ceased the spontaneous ectopic discharges recorded from A beta to C fibers but also blocked the afferent ectopic discharge elicited by K+ channel blocker, noradrenaline, Ca2+ or antidromic stimulation of sciatic nerve proximal to the injured nerve area. The experiments indicated that anisodamine probably possessed a calcium channel blocker-like activity and produced selective block of the new channels in the injured area. It is suggested that anisodamine may be a candidate therapeutic agent in relieving hyperalgesia and allodynia following nerve injury.
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The present study was done to estimate rise in skin temperature during a pain reaction time (pain RT) as a means of investigating why a pricking pain threshold, produced by thermal stimulation using time method, often increases during repeated measurements. The pain RT, or the time-delay between occurrence of pain sensation and a subsequent motor response, was measured by making EMG recording on a forearm. The radiant heat stimuli were three, 200, 300, and 350 mcal/sec./cm2, each of which was given through a round radiation window of an algesiometer head. Analysis showed that the pain RTs would be too short to explain higher pain thresholds often found using the time method.