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Intradermal injection of the capsaicin analogue, NE-21610 (Procter and Gamble), inactivates nociceptors but not low-threshold mechanoreceptors in monkey. The present study examined the effects of cutaneous NE-21610 on heat and mechanical sensation in normal human volunteers. In the first series of experiments, subjects received intradermal (i.d.) injections (30 μl) of the vehicle alone or with the...
Improved methods for pain measurement have both theoretical and clinical importance. This study evaluated the Descriptor Differential Scale (DDS) of Pain Intensity, a recent methodology designed for assessing pain reports in clinical samples. Experiment 1 evaluated the sensitivity of the measure to small changes in electrocutaneous stimulation relative to a traditional visual analogue scale (VAS)...
Cutaneous injection of the capsaicin analog NE-21610 (Procter and Gamble) produces analgesia to heat but not mechanical stimuli in humans. The present study examined whether pretreatment of the skin with NE-21610 prevents the development of hyperalgesia following heat injury. On the 1st day of testing, 7 volunteers received a 30-μl intradermal injection of vehicle to one volar forearm and 10 μg...
Central pain syndromes (CPS) could be caused by disinhibition of spinothalamic excitability or by other central nervous system (CNS) changes caused by reduced spinothalamic function. To examine these possibilities, we studied 11 patients (ages 51-82 years) with unilateral central pain and with reproducible cerebral evoked vertex potentials in response to cutaneous stimulation of the normal side with...
Cutaneous stimulation with CO 2 laser pulses activates A δ nociceptive afferents and evokes late cerebral potentials (LEPs), the amplitude of which correlates parametrically with the perceived magnitude estimation of laser pulses. Capsaicin is known to desensitize the nociceptive terminals of C fibers. In this double-blind, vehicle-controlled experiment, we tested the hypothesis that topical...
Electrophysiological evidence from cutaneous nociceptors suggested a synergism between excitatory actions of inflammatory mediators (IM) and low pH. In human skin it is possible to induce constant ongoing pain with continuous infusion of acid buffer. This method was used to study the interaction with mediators of inflammation psychophysiologically. A skin area on the palmar forearm of 6 subjects (either...
Cervical spinal pain is frequently found in conjuction with idiopathic cervical dystonia (ICD), a focal dystonia characterized by sustained deviation of the head. Since the perception of noxious stimuli has never been studied in ICD, we performed a controlled study to obtain more insight into the psychophysics of dystonia-related muscle pain by evaluating pressure-induced pain levels. In nine ICD...
The present study evaluated the ability of humans to discriminate temperature decreases in the noxious and innocuous cold range. Two groups of five subjects detected changes in cold stimuli applied to the maxillary face. For five subjects, adapting temperatures of 22°, 16°, and 0°C were used, and thresholds for detecting temperature decreases were determined using an adaptive psychophysical paradigm...
The aim of this study was to develop a model of transient hyperalgesia in the awake monkey performing operant tasks. An adult male rhesus monkey was trained to press a lever to receive food reward for detecting a light or to escape mechanical or thermal stimuli applied in the maxillary region of the face. A small contact thermode was positioned on one side of the face and a mechanical stimulator was...
Several aspects of tactile, thermal and pain perception were evaluated in an individual (R.S.) with a hemorrhagic lesion centered in her left lateral thalamus. Over a 4-year period, psychophysical evaluations were undertaken every 6–8 months, and five magnetic resonance (MR) studies were conducted. Early tests (1991–1992) revealed large contralateral deficits in R.S.'s perception of touch, innocuous...
Dorsal horn neurons that respond to noxious cold also respond to noxious heat, suggesting the hypothesis that pain evoked by temperature extremes, whether hot or cold, may be processed similarly in the CNS. In this study, we tested perceptual consequences of this hypothesis by comparing characteristics of heat and cold pain, as well as of innocuous warm and cool. Eight healthy subjects performed psychophysical...
The aim of the study was to examine reproducibility of primary and secondary hyperalgesia in a psychophysical model of human inflammatory pain. Mild burns were produced on the crura of 12 volunteers with a 50 25 mm thermode (47°C, 7 min). Assessments of (i) cold and warm detection thresholds, (ii) mechanical and heat pain thresholds, (iii) pain to heat (43°C and 45°C, 5 s), (iv) secondary hyperalgesia,...
Temporal summation of pain occurs when repeated stimuli become increasingly painful in spite of unchanged stimulus intensity. Summation can be quantified as the difference in pain between the first and the last stimulus in a train of stimuli. The aim of the study was to compare temporal summation of pain in normal skin with summation of pain in skin with primary and secondary hyperalgesia evoked by...
Little is known concerning the mechanisms underlying the perception of cold pain in humans. An appreciation of these mechanisms is important to understand and possibly treat those disorders in which cold stimuli evoke unpleasant sensations. To study cold pain, I have conducted psychophysical experiments on 16 healthy subjects. A peltier-type stimulator (20 25 mm) was used to deliver stimuli to sites...
Recent studies into the common complaint of chronic neck pain have focused on its anatomical origin, identifying especially the cervical zygapophysial joints. However the pathophysiology of chronic neck pain remains poorly understood. In this psychophysical study, responses to electrocutaneous stimulation in subjects with chronic neck pain were examined. In an ascending method of limits design, electrical...
The aim of the study was to examine the presence of hyperalgesia to heat stimuli within the zone of secondary hyperalgesia to punctate mechanical stimuli. A burn was produced on the medial part of the non-dominant crus in 15 healthy volunteers with a 50 x 25 mm thermode (47 o C, 7 min), and assessments were made 70 min and 40 min before, and 0, 1, and 2 h after the burn injury. Hyperalgesia...
Clinicians and researchers often ask patients to remember their past pain. They also use patient's reports of relief from pain as evidence of treatment efficacy, assuming that relief represents the difference between pretreatment pain and present pain. We have estimated the accuracy of remembering pain and described the relationship between remembered pain, changes in pain levels and reports of relief...
Capsaicin applied topically to human skin produces itching, pricking and burning sensations due to excitation of nociceptors. With repeated application, these positive sensory responses are followed by a prolonged period of hypalgesia that is usually referred to as desensitization, or nociceptor inactivation. Consequently, capsaicin has been recommended as a treatment for a variety of painful syndromes...
Sensitization to continued nociceptive stimulation is supposed to be involved in the development of chronic pain at several levels of the CNS, but experimental studies investigating the perceptual dynamics of sensitization in humans are rare, and the diagnostic validity of experimental pain models is not known. The present study used a tonic heat paradigm to assess early sensitization (15-100 s) to...
The psychophysical responses to noxious cold stimulation of the skin in normal human subjects are not well understood. Continuous pain ratings with the visual analogue scale is an important method to assess these responses. In this study, we addressed several important issues about the parameters with which stimuli are delivered: the type of skin stimulated, the rate with which the stimulus temperature...
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