Search results for "Afferent"
showing 10 items of 115 documents
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…
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…
Periodontal Alteration of the Microcirculation and Hypercholesterolemia: A Possible Correlation?
2011
OBJECTIVE: We evaluated the morphological and parametric characteristics of the periodontal microcirculation in patients diagnosed as having hypercholesterolemia and high levels of low-density lipoprotein (LDL). METHODS: Forty patients were recruited, 20 of whom were affected by hypercholesterolemia and 20 of whom were considered healthy. A videocapillaroscopic examination was carried out on the periodontal mucosa in the proximity of the frenulum (II, V sextant). RESULTS: The difference between the parameters of the hypercholesterolemia group and the control group was evaluated with the Mann-Whitney U-test for non-parametric ordinal data; the level of significance being P < 0.05. The videoc…
Perceptual Correlate of Nociceptive Long-Term Potentiation (LTP) in Humans Shares the Time Course of Early-LTP
2006
As in neocortex and hippocampus, neurons in the dorsal horn of the spinal cord develop long-term potentiation of synaptic efficacy (LTP) on high-frequency stimulation (HFS) of their afferent input, although how long LTP lasts in this nociceptive relay nucleus has not yet been addressed. Here we studied neurogenic hyperalgesia, a perceptual correlate of nociceptive LTP, in 13 healthy subjects, after HFS (5 × 1 s at 100 Hz) of superficial cutaneous afferents. HFS led to a mean upward shift of the stimulus–response function for pinprick-evoked pain (punctate mechanical hyperalgesia) in all subjects by a factor of 2.5 ( P < 0.001) that lasted undiminished for the initial 1-h observation per…
Cerebral potentials elicited by mechanical stimuli to the human leg: influence of artifacts
1992
Mechanical stimulation with a reflex hammer was applied to the quadriceps muscle tendon of healthy volunteers and patients. The time-locked electrical signals were recorded from the scalp. In all cases, reproducible potentials could be recorded, with latencies in a range of 20 ms to 100 ms. The potentials recorded in patients under complete spinal anesthesia were similar to those derived before the anesthesia. In brain dead patients who showed absence of median nerve or posterior tibial nerve SEP, reproducible potentials after mechanical stimuli could be recorded as well. The results suggest that the hammer taps lead to mechanical shock waves which are propagated along the body producing ti…
GAA trinucleotide repeat expansion in variant Friedreich's ataxia families.
1997
Phenotypic variants in Friedreich's ataxia include late onset, preservation of the lower limbs tendon reflexes, and slow progression. We describe clinical and electrophysiological features from three families with Friedreichlike phenotypes. Friedreich's ataxia diagnosis was confirmed by finding two allelic expansions of the GAA trinucleotide repeat at the X25 gene. In family 1 both patients had a late-onset phenotype with preservation of knee and ankle jerks, lack of cardiomyopathy, and preserved H reflex. One of them did not have electrophysiologic evidence of sensory axonal neuropathy. Patients from family 2 showed variability in the age of onset, and 2 out of 3 affected children had hype…
Effects of long- and short-term fatiguing stretch-shortening cycle exercises on reflex EMG and force of the tendon-muscle complex
2003
This study examined the fatigue effects of stretch-shortening cycle exercises of different intensity and duration on stretch reflex EMG and mechanical responses of the triceps surae muscle. Twelve subjects performed either a 10-km run ( n=6) or short but exhaustive rebound exercise on a sledge apparatus ( n=6). Passive reflex tests (mechanically induced ankle dorsiflexions) were examined before, after as well as 2 h, 2 and 7 days after exercise. Mechanical reflex responses were recorded from the ergometer torque signal. An acute contractile failure was observed as large reductions in twitch responses, especially in the sledge subgroup who showed high post-exercise peak blood lactate and an …
Spreading of sudomotor axon reflexes in human skin.
2005
Acetylcholine (ACh) activates both sudomotor fibers and primary afferent nociceptors. This leads to sudomotor and vasodilator axon reflexes, which can be diminished, for example, in neuropathies. In some neuropathies, however, there is increased axon reflex sweating, a response pattern that has never been observed for vasodilator flares.To compare both types of axon reflexes and to elucidate possible differences.In healthy young male subjects, sweat response and flare reaction in response to ACh were quantified. Constant-current iontophoresis (300 mC) of ACh was performed on the lateral lower legs. The sudomotor axon reflex was visualized with iodine starch staining, and the sweat response …
Cardiac modulation of startle is altered in depersonalization-/derealization disorder: Evidence for impaired brainstem representation of baro-afferen…
2016
Patients with depersonalization-/derealization disorder (DPD) show altered heartbeat-evoked brain potentials, which are considered psychophysiological indicators of cortical representation of visceral-afferent neural signals. The aim of the current investigation was to clarify whether the impaired CNS representation of visceral-afferent neural signals in DPD is restricted to the cortical level or is also present in sub-cortical structures. We used cardiac modulation of startle (CMS) to assess baro-afferent signal transmission at brainstem level in 22 DPD and 23 healthy control individuals. The CMS paradigm involved acoustic startle stimuli (105dB(A), 50ms) elicited 0, 100, 200, 300, 400 and…
Different short-term modulation of cortical motor output to distal and proximal upper-limb muscles during painful sensory nerve stimulation
2004
The pattern of upper-limb muscle activation following painful stimulation has not been clarified in detail. We investigated the short-term inhibitory and excitatory effects of painful electrical digital stimulation on the motoneuron pools of distal and proximal upper-limb muscles. Transcranial magnetic stimulation (TMS) was used as test stimulus, and painful digital nerve stimulation as conditioning stimulus for motor evoked potential (MEP) recordings over the abductor digiti minimi (ADM), abductor pollicis brevis (APB), biceps brachii (BB), and deltoid muscles. Inhibition of the conditioned MEP response was most prominent in the distal muscles, whereas BB and deltoid muscles were only weak…