New Developments in Microneurography of Human C Fibers

Physiology ◽  
1996 ◽  
Vol 11 (4) ◽  
pp. 170-175
Author(s):  
C Forster ◽  
M Schmelz
Keyword(s):  
Conduction Velocity ◽  
Refractory Period ◽  
Nerve Fibers ◽  
Cutaneous Nerve ◽  
New Developments ◽  
Relative Refractory Period ◽  
C Fibers ◽  
Highly Sensitive ◽  
Different Types

Slowing of conduction velocity during the relative refractory period of an axon can be used to detect activation in human cutaneous nerve fibers. The method is highly sensitive and provides the means to identify individual unmyelinated afferent and efferent (sympathetic) units excited by different types of stimuli.

Conduction velocity in unmyelinated nerve fibers of a cutaneous nerve

1973 ◽  
Vol 76 (3) ◽  
pp. 1004-1007 ◽  
Author(s):  
A. V. Zeveke ◽  
V. I. Myaderov ◽  
V. A. Utkin ◽  
V. L. Shaposhnikov
Keyword(s):  
Conduction Velocity ◽  
Nerve Fibers ◽  
Cutaneous Nerve ◽  
Unmyelinated Nerve

Preferential Block of Small Myelinated Sensory and Motor Fibers by Lidocaine

2001 ◽  
Vol 95 (6) ◽  
pp. 1441-1454 ◽  
Author(s):  
Alexander P. Gokin ◽  
Benjamin Philip ◽  
Gary R. Strichartz
Keyword(s):  
Sciatic Nerve ◽  
Conduction Velocity ◽  
Differential Susceptibility ◽  
Nerve Fibers ◽  
Motor Deficits ◽  
Sprague Dawley ◽  
Size Principle ◽  
Functional Deficits ◽  
Myelinated Fibers ◽  
C Fibers

Background Controversy still surrounds the differential susceptibility of nerve fibers to local anesthetics and its relation to selective functional deficits. In the current study we report features of conduction blockade in different classes of rat sciatic nerve fibers after injection of lidocaine by a percutaneous procedure that closely resembles clinical applications. Methods In 30 adult male Sprague-Dawley rats (weight, 300-400 g) during general anesthesia, impulses were recorded in different classes of sensory axons (large, Aalpha and beta fibers; small, Adelta myelinated fibers and unmyelinated C fibers) and motor axons (large, Aalpha fibers; small, Agamma myelinated fibers) classified by conduction velocity. The sciatic nerve was stimulated distally, and impulses were recorded from small filaments teased from L4-L5 dorsal (sensory) and ventral (motor) roots sectioned acutely from the spinal cord. Lidocaine at concentration of 0.05-1% was injected percutaneously in 0.1-ml solutions at the sciatic notch. Both tonic (stimulated at 0.5 Hz) and use-dependent (stimulated at 40 Hz for Adelta and Agamma fibers and at 5 Hz for C fibers) impulse inhibitions by lidocaine were assayed. Results Minimal effective (threshold) lidocaine concentrations (i.e., to block conduction in 10% of fibers) were, for sensory, 0.03% for Adelta, 0.07% for Aalphabeta, and 0.09-0.1% for C fibers, and for motor, 0.03% for Agamma and 0.05% for Aalpha fibers. The order of fiber susceptibility, ranked by concentrations that gave peak tonic fiber blockade of 50% (IC50s), was Agamma > Adelta = Aalpha > Aalphabeta > C. Faster-conducting C fibers (conduction velocity > 1 m/s) were more susceptible (IC50 = 0.13%) than slower ones (conduction velocity < 1 m/s; IC50 = 0.30%). At 1% lidocaine, all fibers were tonically blocked. Use-dependent effects accounted for only a modest potentiation of block (at a lidocaine concentration of 0.25%) in Adelta and Agamma fibers, and in C fibers phasic stimulation had even smaller effects and sometimes relieved tonic block. Conclusions Susceptibility to lidocaine does not strictly follow the "size principle" that smaller (slower) axons are always blocked first. This order of fiber blockade is qualitatively consistent with previous reports of the order of functional deficits in the rat after percutaneous lidocaine, that is, motor = proprioception > nociception, if we assume that motor deficits first arise from conduction failure in Agamma fibers and that nociception relies on C fiber conduction.

Excitation and Conduction in Immature Nerve Fibers of the Developing Chick

1957 ◽  
Vol 190 (2) ◽  
pp. 371-376 ◽  
Author(s):  
F. G. Carpenter ◽  
R. M. Bergland
Keyword(s):  
Linear Relationship ◽  
Conduction Velocity ◽  
Light Microscope ◽  
Adult Stage ◽  
Fiber Diameter ◽  
Fold Increase ◽  
Nerve Fibers ◽  
Velocity Correlation ◽  
C Fibers ◽  
Sciatic Nerves

The velocity of impulse transmission in sciatic nerves dissected from fetal chicks has been measured at various stages of development. From day 10 through the adult stage an 80-fold increase in conduction velocity has been observed. The linear velocities of the fastest components are 0.5 m/sec. at day 10, 7–11 m/sec. at day 21, and 50 m/sec. in the adult. In immature nerve prior to myelination ( day 10) at least two components of different velocities may be recognized. Spike potentials at day 16 are almost identical in form to the A complex of the adult although the rate of propagation is slower. Potential changes that are believed to be associated with transmission in C fibers are visible at day 16. During development the increase in conduction velocity which was observed was concomitant with the deposition of myelin and when the velocity was increasing most rapidly, the process of myelination was found to be most active. A linear relationship between fiber diameter and CV has been observed only in the juvenile and adult forms. Microscopically the nerve fibers appear to be unmyelinated at day 10-day 14 and at the time of hatching myelination is rather extensive. Before day 15 it was impossible to make a diameter/velocity correlation since measurements with the light microscope are inaccurate below 1µ.

scholarly journals Streptococcus pyogenes vulvovaginitis in children in Nottingham

1991 ◽  
Vol 106 (3) ◽  
pp. 459-465 ◽  
Author(s):  
F. E. Donald ◽  
R. C. B. Slack ◽  
G. Colman
Keyword(s):  
Public Health ◽  
Streptococcus Pyogenes ◽  
Public Health Laboratory ◽  
Large Numbers ◽  
Highly Sensitive ◽  
Vaginal Swabs ◽  
Different Types ◽  
Winter Peak ◽  
The Common

SUMMARYIsolates of Streptococcus pyogenes from vaginal swabs of children with vulvovaginitis received at Nottingham Public Health Laboratory during 1986–9 were studied. A total of 159 isolates was made during the 4 years, increasing from 17 in 1986 to 64 in 1989 and accounting for 11% of all vaginal swabs received from children. The numbers of throat swabs yielding S. pyogenes also showed an increase from 974 in 1986 to 1519 in 1989. A winter peak of isolates was noted for both vaginal swabs and throat swabs. A total of 98 strains from vaginal swabs were serotyped: 22 different types were identified, 61% of which were the common types M4, M6, R28 and M12. Erythromycin sensitivity was done on 89 strains; 84% were highly sensitive (MIC < 0·03 mg/1). There are no other reports of such large numbers in the literature; the reason for seeing this increase in Nottingham is unclear.

Activity-dependent variations in conduction velocity of C fibers of rat sciatic nerve

1994 ◽  
Vol 19 (4) ◽  
pp. 427-431 ◽  
Author(s):  
Hyung-Cheul Shin ◽  
Yun-Lyul Lee ◽  
Hyeok-Yil Kwon ◽  
Hyoung Jin Park ◽  
Stephen A. Raymond
Keyword(s):  
Sciatic Nerve ◽  
Conduction Velocity ◽  
Rat Sciatic Nerve ◽  
C Fibers ◽  
Activity Dependent

scholarly journals A new function for ATP: activating cardiac sympathetic afferents during myocardial ischemia

2010 ◽  
Vol 299 (6) ◽  
pp. H1762-H1771 ◽  
Author(s):  
Liang-Wu Fu ◽  
John C. Longhurst
Keyword(s):  
Myocardial Ischemia ◽  
Cardiovascular Responses ◽  
P2 Receptors ◽  
Nerve Fibers ◽  
Disulfonic Acid ◽  
Dependent Manner ◽  
P2 Receptor ◽  
C Fibers ◽  
Spinal Afferents ◽  
Cardiac Afferents

Myocardial ischemia activates cardiac sympathetic afferents leading to chest pain and reflex cardiovascular responses. Brief myocardial ischemia leads to ATP release in the interstitial space. Furthermore, exogenous ATP and α,β-methylene ATP (α,β-meATP), a P2X receptor agonist, stimulate cutaneous group III and IV sensory nerve fibers. The present study tested the hypothesis that endogenous ATP excites cardiac afferents during ischemia through activation of P2 receptors. Nerve activity of single unit cardiac sympathetic afferents was recorded from the left sympathetic chain or rami communicates (T2-T5) in anesthetized cats. Single fields of 45 afferents (conduction velocities = 0.25–4.92 m/s) were identified in the left ventricle with a stimulating electrode. Five minutes of myocardial ischemia stimulated 39 of 45 cardiac afferents (8 Aδ, 37 C fibers). Epicardial application of ATP (1–4 μmol) stimulated six ischemically sensitive cardiac afferents in a dose-dependent manner. Additionally, epicardial ATP (2 μmol), ADP (2 μmol), a P2Y agonist, and α,β-meATP (0.5 μmol) significantly activated eight other ischemically sensitive afferents. Third, pyridoxal phosphate-6-azophenyl-2′,4′-disulfonic acid, a P2 receptor antagonist, abolished the responses of six afferents to epicardial ATP (2 μmol) and attenuated the ischemia-related increase in activity of seven other afferents by 37%. In the absence of P2 receptor blockade, cardiac afferents responded consistently to repeated application of ATP ( n = 6) and to recurrent myocardial ischemia ( n = 6). Finally, six ischemia-insensitive cardiac spinal afferents did not respond to epicardial ATP (2–4 μmol), although these afferents did respond to epicardial bradykinin. Taken together, these data indicate that, during ischemia, endogenously released ATP activates ischemia-sensitive, but not ischemia-insensitive, cardiac spinal afferents through stimulation of P2 receptors likely located on the cardiac sensory neurites.

Comparison of responses of warm and nociceptive C-fiber afferents in monkey with human judgments of thermal pain

1978 ◽  
Vol 41 (2) ◽  
pp. 509-528 ◽  
Author(s):  
R. H. LaMotte ◽  
J. N. Campbell
Keyword(s):  
Skin Temperature ◽  
Conduction Velocity ◽  
Mechanical Stimulation ◽  
Human Subjects ◽  
Radiant Heat ◽  
Cumulative Number ◽  
Painful Stimulation ◽  
C Fibers ◽  
Nociceptive Afferents ◽  
Stimulus Temperature

1. Radiant-heat stimuli of different intensities were delivered every 28 s to the thenar eminence of the hand of human subjects and to the receptive fields (RFs) of 58 "mechanothermal nociceptive" and 16 "warm" C-fibers, most of which innervated the glabrous skin of the monkey hand. A CO2 infrared laser under control via a radiometer provided a step increase in skin temperature to a level maintained within +/- 0.1 degrees C over a 7.5-mm-diameter spot. 2. Human subjects categorized the magnitude of warmth and pain sensations evoked by stimuli that ranged in temperature from 40 to 50 degrees C. The scale of subjective thermal intensity constructed from these category estimates showed a monotonically increasing relation between stimulus temperature and the magnitude of warmth and pain sensations. 3. The mechanothermal fibers had a mean RF size of 18.9 +/- 3.2 mm2 (SE), a mean conduction velocity of 0.8 +/- 0.1 m/s, mean thresholds of 43.6 +/- 0.6 degrees C for radiant heat and 5.95 +/- 0.59 bars for mechanical stimulation, and no spontaneous activity. In contrast, warm fibers had punctate RFs, a mean conduction velocity of 1.1 +/- 0.1 m/s, heat thresholds of less than 1 degrees C above skin temperature, no response to mechanical stimulation, and a resting level of activity in warm skin that was suppressed by cooling. 4. The cumulative number of impulses evoked during each stimulation in the nociceptive afferents increased monotonically as a function of stimulus temperature over the range described by humans as increasingly painful (45-50 degrees C). Nociceptive fibers showed little or no response to stimulus temperatures less than 45 degrees C that elicited in humans sensations primarily of warmth but not pain. In contrast, the cumulative impulse count during stimulation of each warm fiber increased monotonically with stimulus temperature over the range of 39-43 degrees C. However, for stimuli of 41-49 degrees C the cumulative impulse count in warm fibers was nonmonotonic with stimulus temperature. Warm-fiber response to stimuli of 45 degrees C or greater usually consisted of a short burst of impulses followed by cessation of activity. 5. The subjective magnitude of warmth and pain sensations in humans and the cumulative impulse count evoked by each stimulus in warm and nociceptive afferents varied inversely with the number, delivery rate, and intensity of preceding stimulations. 6. The results of these experiments suggest the following: a) that activity in the mechanothermal nociceptive C-fibers signals the occurrence of pain evoked by radiant heat, and that the frequency of discharge in these fibers may encode the intensity of painful stimulation; b) that activity in warm fibers may encode the intensity of warmth at lower stimulus temperatures, but is unlikely to provide a peripheral mechanism for encoding the intensity of painful stimulation at higher stimulus temperatures.

scholarly journals New Developments in Scanning Microelectrochemical Techniques: A Highly Sensitive Route to Evaluate Degradation Reactions and Protection Methods with Chemical Selectivity

2018 ◽  
Vol 875 ◽  
pp. 19-23
Author(s):  
Ricardo M. Souto ◽  
Dániel Filotás ◽  
Bibiana M. Fernández-Pérez ◽  
Lívia Nagy ◽  
Géza Nagy
Keyword(s):  
Galvanized Steel ◽  
New Developments ◽  
Saline Environment ◽  
Spatially Resolved ◽  
Degradation Reactions ◽  
Ion Distributions ◽  
Scanning Electrochemical Microscope ◽  
Highly Sensitive ◽  
Chemical Selectivity

The scanning electrochemical microscope (SECM) offers a highly sensitive route to evaluate degradation reactions and protection methods with chemical selectivity by using ion-selective microelectrodes as tips, thus operating SECM potentiometrically. Spatially resolved imaging of electrochemical reactivity related to each component of the investigated material can thus be effectively monitored selectively both in situ and in real time. The applicability of this method has been illustrated using a practical example of a metal-coating system, consisting in the exposure of cut edges of coil-coated galvanized steel to aqueous saline environment. In this contribution, localized pH and zinc(II) ion distributions originated around cut edges of coil coated steel immersed in 1 mM NaCl solution are shown.

Development of spontaneous activity and mechanosensitivity in axotomized afferent nerve fibers during the first hours after nerve transection in rats

1995 ◽  
Vol 74 (3) ◽  
pp. 1020-1027 ◽  
Author(s):  
M. Michaelis ◽  
K. H. Blenk ◽  
W. Janig ◽  
C. Vogel
Keyword(s):  
Spontaneous Activity ◽  
Discharge Rate ◽  
Nerve Fibers ◽  
Nerve Lesion ◽  
Nerve Transection ◽  
Unmyelinated Fibers ◽  
C Fibers ◽  
Afferent Nerve Fibers ◽  
Irregular Frequency ◽  
The Mean

1. Spontaneous activity and ectopic mechanical excitability of axotomized unmyelinated and myelinated fibers in the sural nerve were examined in anesthetized rats. The analysis was performed within 30 h after the nerve lesion using single-fiber recordings that were performed proximal to the severed nerve end. 2. Among all unmyelinated fibers tested (n = 865), 4-8% exhibited persistent spontaneous activity of low and irregular frequency. The percentage of spontaneously active C fibers did not change significantly during the first 30 h. Only 6 of 796 A fibers had spontaneous activity. 3. Mechanical stimulation of the cut nerve end excited 5-8% of all C fibers under investigation. No development with time could be detected in the frequency of mechanically excitable C fibers. In contrast, beginning 6 h after nerve transection, the number of mechanically excitable A fibers rose with time, reaching 27% after 22-30 h. 4. Among the A fibers (C fibers) that exhibited mechanical excitability or spontaneous activity, only 4% (25%) had both properties, whereas 96% (75%) were either mechanosensitive or spontaneously active. 5. With time after the nerve lesion, the mean discharge rate of all spontaneously discharging C fibers decreased significantly from 49 imp/min (0.5-9 h after nerve lesion) to 11 imp/min after 22-30 h. The mean discharge rate of C fibers exhibiting solely spontaneous activity and those C fibers that were additionally mechanosensitive did not differ significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

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