Pain
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The submaximum effort tourniquet technique (SETT) is becoming more widely used as part of the clinical assessment of chronic pain patients despite little information about the scaling of this technique. Ratio scaling procedures resulted in a linear function, presumed to underlie clinical application of the SETT, for only 11% of the subjects. ⋯ Differences in these growth curves are discussed with reference to the concept of pain endurance. Continued needs for standardized pain evaluation techniques suggest that this type of psychophysical scaling procedure may improve the precision of some clinical pain assessments.
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(1) Sixty-eight convergent dorsal horn neurones have been recorded at the lumbar level in anaesthetized intact rats. All cells received prominent A alpha and C fibre afferents and correspondingly could be activated by high and low threshold stimuli applied to the peripheral excitatory receptive field. (2) The activity of 67/68 of these neurones was powerfully inhibited by noxious stimuli applied to various parts of the body. Since non-noxious stimuli were ineffective in this respect, the term "diffuse noxious inhibitory controls" (DNIC) is proposed. (3) DNIC could be evoked by noxious pinch applied to the tail, the contralateral hind paw, the forepaws, the ears and the muzzle; the most effective areas were the tail and muzzle. Noxious heat applied to and transcutaneous electrical stimulation of the tail were extemely effective in eliciting DNIC as was the intraperitoneal injection of bradykinin. (4) DNIC strongly depressed by 60-100% both the C fibre response following suprathreshold transcutaneous electrical stimulation and the responses to noxious radiant heat. (5) The spontaneous activity and the responses to low threshold afferents induced either by A alpha threshold electrical or natural stimulation were also powerfully inhibited. (6) In the majority of cases, long lasting post-effects directly related to the duration of conditioning painful stimulus were observed.
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The submaximal effort tourniquet test has been widely used to evaluate experimental and chronic pain; however, there has been great variation in the manner in which the test has been applied. The present study systemitically evaluates how different levels of exercise duration and effort affect subjects' report of pain. The data indicate the following: (1) the manner in which the exercise is performed has an important effect on subjects' rating of pain, and (2) under all conditions studied, the pain ratings do not increase as a linear function of time. Both findings warrant precautions when using the submaximal effort tourniquet test to study experimental and chronic pain.
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Electrical potentials evoked by 5 intensities of painful dental stimulation were recorded at the scalp. During testing, volunteers indicated subjective painfulness by verbal pain ratings and visual analogue scales. Evoked potentials (EPs) to each intensity, observed between 50 and 400 msec, were characterized by 4 waveform components. ⋯ In contrast, the amplitudes of the two later components were associated with subjective painfulness but not with stimulus intensity. A strong linear relationship was observed between subjective painfulness and peak-to-peak amplitude for the EP component observed between 175 and 260 msec. The data suggest that the earlier EP components may reflect sensory transmission processes while the later components indicate brain activity when pain is perceived.