Search results for "CICE"
showing 10 items of 312 documents
Nociceptive masseter inhibitory reflexes evoked by laser radiant heat and electrical stimuli
1997
Electrical stimulation of the mental nerve evokes two suppression periods SP1 and SP2 in masseter muscle activity bilaterally. In order to investigate a possible nociceptive origin of the suppression periods, we compared the reflex responses evoked by electrical stimulation and by selective activation of nociceptors in hairy skin using painful infrared laser stimuli. The SP was elicited during more than 90% maximal voluntary contraction. Thresholds for detection, pain, and SP in the mental nerve area were determined by the method of limits. A suppression period was evoked by laser stimuli in nine of ten subjects bilaterally. The mean onset latency was 46.9 ms, the mean duration 58.9 ms. The…
Perceptual correlates of nociceptive long-term potentiation and long-term depression in humans.
2004
Long-term potentiation (LTP) and long-term depression (LTD) of synaptic strength are ubiquitous mechanisms of synaptic plasticity, but their functional relevance in humans remains obscure. Here we report that a long-term increase in perceived pain to electrical test stimuli was induced by high-frequency electrical stimulation (HFS) (5 × 1 sec at 100 Hz) of peptidergic cutaneous afferents (27% above baseline, undiminished for >3 hr). In contrast, a long-term decrease in perceived pain (27% below baseline, undiminished for 1 hr) was induced by low-frequency stimulation (LFS) (17 min at 1 Hz). Pain testing with punctate mechanical probes (200 μm diameter) in skin adjacent to the HFS–LFS con…
Modality-specific sensory changes in humans after the induction of long-term potentiation (LTP) in cutaneous nociceptive pathways.
2007
The impact of long-term potentiation (LTP) in nociceptive pathways on somatosensory perception was examined by means of quantitative sensory testing (QST) in the ventral forearm of 12 healthy human subjects. Electrical high-frequency stimulation of the forearm skin (HFS; 5 x 1 s at 100 Hz and 10 x detection threshold) led to an abrupt increase of pain to single electrical test stimuli, which were applied through the same electrode (perceptual LTP +72%, p0.01). Perceptual LTP outlasted the 1-h observation period. The effects of HFS on somatosensory perception of natural test stimuli in the conditioned skin area were restricted to mechanical submodalities. Subjects exhibited a significant dec…
Effects of the NMDA-receptor antagonist ketamine on perceptual correlates of long-term potentiation within the nociceptive system
2007
We recently reported perceptual correlates of long-term potentiation (LTP) of synaptic strength within the nociceptive system demonstrating the functional relevance of LTP for human pain sensation. LTP is generally classified as NMDA-receptor dependent or independent. Here we show that low doses of the NMDA-receptor antagonist ketamine (0.25 mg/kg) prevented the long-term increase in perceived pain to electrical test stimuli, which was induced by high-frequency electrical stimulation (HFS) of nociceptive afferents. Whereas in a control experiment HFS led to a stable increase in perceived pain by 51% for the entire observation period of 1 h HFS given 4 min after i.v. ketamine was ineffective…
Zolmitriptan inhibits neurogenic inflammation and pain during electrical stimulation in human skin.
2014
Background Triptans are agonists to 5-HT 1B/D/F receptors, which are present on nociceptive neurons not only within but also beyond the trigeminal system. The aim of this study was to investigate whether zolmitriptan interacts with peptidergic nociceptive afferents in human skin. Methods Twenty participants (13 women, median age: 25; interquartile range: 23–26 years) entered the randomized, double-blind, cross-over study. Electrically induced neurogenic flare and pain was assessed after either placebo or zolmitriptan on the ventral thigh. Mechanical pain thresholds were investigated at baseline and after electrical stimulation at the stimulation site. Results The size of the neurogenic flar…
Activation of the cortical pain network by soft tactile stimulation after injection of sumatriptan.
2006
The anti-migraine drug sumatriptan often induces unpleasant somatosensory side effects, including a dislike of being touched. With a double-blind cross-over design, we studied the effects of sumatriptan and saline on perception (visual analogue scale) and cortical processing (functional magnetic resonance imaging) of tactile stimulation in healthy subjects. Soft brush stroking on the calf (n = 6) was less pleasant (p < 0.04) and evoked less activation of posterior insular cortex in the sumatriptan compared to the saline condition. Soft brushing activated pain processing regions (anterior insular, lateral orbitofrontal, and anterior cingulate cortices, and medial thalamus) only in the sumatr…
Deep pain thresholds in the distal limbs of healthy human subjects.
2003
Pressure pain thresholds (PPTs) in distal limbs have been under-investigated despite their potential clinical importance. Therefore, we compared PPTs over nail bed, bony prominences, and muscle in distal parts of upper and lower limbs. We investigated 12 healthy subjects using three handheld devices: a spring-loaded, analogue pressure threshold meter (PTM) with two operating ranges, and an electronic Algometer. PPTs were determined with three series of ascending stimulus intensities with a ramp of about 50 kPa/s. PPTs were normally distributed in logarithmic space. PPTs over different tissues varied significantly (ANOVA, p0.001): mean thresholds and 95% confidence intervals were 615 kPa (26…
Spatial discrimination thresholds for pain and touch in human hairy skin
2001
The traditional concept that pain is poorly localized has been challenged by recent studies, where subjects were able to point to the stimulated spot on the skin with an accuracy of 10-20 mm. Pointing movements themselves, however, have errors of about 15 mm. To determine the limits of sensory performance of the nociceptive system independent of motor performance, point localization of heat pain (540 mJ punctate laser stimuli, 5 mm diameter), mechanical pain (256 mN punctate probe, 200 microm diameter), and touch (16 mN von Frey probe, 1.1 mm diameter) were tested in a two-alternative forced-choice paradigm in 12 healthy subjects. Stimuli were applied in randomized order to two parallel lin…
Clinical evaluation criteria for the assessment of impaired pain sensitivity by thulium-laser evoked potentials
2000
Abstract Objectives : Cortical potentials evoked by carbon dioxide laser pulses have been applied in clinical practice to study nociceptive pathways for several years. In this study, we evaluate the properties of an infrared laser (thulium-YAG) with a penetration depth in the skin that matches the intracutaneous depth of nociceptors. Methods : Temperature measurements and modelling showed that the thulium laser generates painful intracutaneous temperatures with less surface heating than the carbon dioxide laser and with no side effects (up to 600 mJ pulse energy). To develop clinical evaluation criteria, laser-evoked potentials (LEPs) were recorded from 3 midline positions (Fz, Cz, Pz) vers…
Numbness in clinical and experimental pain – A cross-sectional study exploring the mechanisms of reduced tactile function
2008
Pain patients often report distinct numbness of the painful skin although no structural peripheral or central nerve lesion is obvious. In this cross-sectional study we assessed the reduction of tactile function and studied underlying mechanisms in patients with chronic pain and in healthy participants exposed to phasic and tonic experimental nociceptive stimulation. Mechanical detection (MDT) and pain thresholds (MPT) were assessed in the painful area and the non-painful contralateral side in 10 patients with unilateral musculoskeletal pain. Additionally, 10 healthy participants were exposed to nociceptive stimulation applied to the volar forearms (capsaicin; electrical stimulation, twice e…