scholarly journals THE POSTSPIKE POSITIVITY OF UNMEDULLATED FIBERS OF DORSAL ROOT ORIGIN

1958 ◽  
Vol 41 (4) ◽  
pp. 613-632 ◽  
Author(s):  
Herbert S. Gasser
Keyword(s):  
Action Potential ◽  
Dorsal Root ◽  
Nerve Fibers ◽  
Positive Potential ◽  
Apparent Increase ◽  
C Fibers ◽  
Large Size ◽  
New Findings ◽  
Supernormal Period ◽  
The Difference

The positivity following the spike in the action potential of unmedullated nerve fibers of dorsal root origin (d.r.C) has been shown to be homologous with the first positive potential (P1) of other varieties of nerve fibers. Thus it is only through the large size of the positivity that this group of nerve fibers is set apart from other groups. New findings accentuate and make more explicit the difference of d.r.C fiber behavior from that of the sympathetic unmedullated fibers. Support of the conclusion is derived from re-examination of the A fibers as well as from observations on the d.r.C fibers. Increase in size of the P1's in a tetanus of the d.r.C fibers can occur if the frequency is high enough; and it does not occur in an A fiber tetanus if the frequency is low enough. Frequency is also critical in the obtainment of increasing P1's in a tetanus of sympathetic C fibers. Decrease in the size of the P1's in the course of a tetanus is attributable to development of the negative after-potential (N a-p). In rested d.r.C fibers the N a-p is latent. But it appears during a tetanus, develops in size, and after the tetanus leads to a long lasting and clearly defined second positive potential. Absence of a supernormal period during the N a-p of the d.r.C fibers is accounted for. An analysis is made of the apparent increase in size of the spike elevations during a tetanus, for the two subgroups of the C fibers. The difference between the after-potentials of A fibers and of sympathetic C fibers is correlated with the shapes of the curves of cathodal electrotonus of these fibers.

scholarly journals Selective inhibition of vagal afferent nerve pathways regulating cough using Nav 1.7 shRNA silencing in guinea pig nodose ganglia

2013 ◽  
Vol 304 (11) ◽  
pp. R1017-R1023 ◽  
Author(s):  
Yukiko Muroi ◽  
Fei Ru ◽  
Yang-Ling Chou ◽  
Michael J. Carr ◽  
Bradley J. Undem ◽  
...  
Keyword(s):  
Action Potential ◽  
Guinea Pigs ◽  
Fluorescent Protein ◽  
Nerve Fibers ◽  
Vagal Nerve ◽  
Afferent Nerve ◽  
Tracheal Mucosa ◽  
C Fibers ◽  
Nodose Ganglia ◽  
Vagal Afferent

Adeno-associated virus delivery systems and short hairpin RNA (shRNA) were used to selectively silence the voltage-gated sodium channel NaV 1.7 in the nodose ganglia of guinea pigs. The cough reflex in these animals was subsequently assessed. NaV 1.7 shRNA was delivered to the majority of nodose ganglia neurons [50–60% transfection rate determined by green fluorescent protein (GFP) gene cotransfection] and action potential conduction in the nodose vagal nerve fibers, as evaluated using an extracellular recording technique, was markedly and significantly reduced. By contrast, <5% of neurons in the jugular vagal ganglia neurons were transfected, and action potential conduction in the jugular vagal nerve fibers was unchanged. The control virus (with GFP expression) was without effect on action potential discharge and conduction in either ganglia. In vivo, NaV 1.7 silencing in the nodose ganglia nearly abolished cough evoked by mechanically probing the tracheal mucosa in anesthetized guinea pigs. Stimuli such as capsaicin and bradykinin that are known to stimulate both nodose and jugular C-fibers evoked coughing in conscious animals was unaffected by NaV 1.7 silencing in the nodose ganglia. Nodose C-fiber selective stimuli including adenosine, 2-methyl-5-HT, and ATP all failed to evoke coughing upon aerosol challenge. These results indicate that cough is independently regulated by two vagal afferent nerve subtypes in guinea pigs, with nodose Aδ fibers regulating cough evoked mechanically from the trachea and bradykinin- and capsaicin-evoked cough regulated by C-fibers arising from the jugular ganglia.

scholarly journals UNMEDULLATED FIBERS ORIGINATING IN DORSAL ROOT GANGLIA

1950 ◽  
Vol 33 (6) ◽  
pp. 651-690 ◽  
Author(s):  
Herbert S. Gasser
Keyword(s):  
Action Potential ◽  
Dorsal Root Ganglia ◽  
Dorsal Root ◽  
High Sensitivity ◽  
Compound Action Potential ◽  
Sympathetic Ganglia ◽  
Base Line ◽  
Positive Potential ◽  
Histological Data ◽  
Compound Action

The compound action potential of the unmedullated fibers arising from dorsal root ganglia, as recorded in cat skin nerves after conduction of simultaneously initiated impulses, shows among its components a temporal dispersion corresponding to velocities between 2.3 and 0.7 M.P.S. The maximum representation of the component velocities is at about 1.2 M.P.S. On both sides of the maximum the representation falls off irregularly, in such a way that groupings in the distribution produce in the action potential a configuration in which successive features appear always in the same positions at a given conduction distance. Through this demonstration of a characteristic configuration the system of the unmedullated fibers is brought into analogy with that of the medullated fibers. The unmedullated fibers originating in the dorsal root ganglia have distinctive physiological properties, among which is a large positive potential which reaches its maximum immediately after the spike and decrements to half relaxation in about 50 msec., at 37°C. The positive phases of the unit potentials in the compound action potential, owing to their duration, sum to a much greater extent than the temporally dispersed spikes; and, since they have sizes such that one equivalent to 25 per cent of the spike height would not be at the limit, in the summation process the major portion of the compound action potential is caused to be written at a potential level positive to the starting base line. The position of the spikes in the sequence can be seen in the analyses in Section III. The course of the activity in unit fibers is subject to variation in ways affecting the positive potential. Preliminary descriptions, based on orienting experiments, of how these variations are conditioned are given in Section I. Two of the findings are particularly noteworthy. One is the high sensitivity of the dimensions of the postspike positivity to temperature in the range of temperatures at which skin nerves may be expected to function, even when the environmental temperatures of an animal are moderate. The other is the high sensitivity to conditioning by previous activity. The positivity is first decreased, then replaced by a negative potential of similar duration. Reasons have been given why it is inadvisable at the present time to call the postspike potential an after-potential. A comparison has been made of the properties of the unmedullated fibers arising from dorsal root ganglia with those of fibers arising from sympathetic ganglia. The differences are so great that, in the interest of precision in designation, a division of the C group of fibers into two subgroups is indicated. It is suggested that the two subgroups be named respectively d.r.C and s.C. Measurements have been made of the diameters of the d.r.C fibers in a saphenous nerve stained with silver. Graphs showing the number of fibers at each diameter are presented in Section II. In Section III there are shown constructions, from histological data, of the action potential as it would appear, after 3 cm. of conduction, with the correlation between diameter and velocity in strict linearity. The degree of fit between the constructed and recorded potentials can be seen in Fig. 18.

scholarly journals Excitation Properties of Computational Models of Unmyelinated Peripheral Axons

2020 ◽  
Author(s):  
Nicole A Pelot ◽  
David C. Catherall ◽  
Brandon J. Thio ◽  
Nathan D. Titus ◽  
Edward D. Liang ◽  
...  
Keyword(s):  
Experimental Data ◽  
Action Potential ◽  
Computational Models ◽  
Compartment Model ◽  
Nerve Fibers ◽  
Vagal Afferents ◽  
C Fibers ◽  
Unmyelinated Axons ◽  
Potential Shape ◽  
Single Compartment Model

Biophysically-based computational models of nerve fibers are important tools for designing electrical stimulation therapies, investigating drugs that affect ion channels, and studying diseases that affect neurons. Although peripheral nerves are primarily composed of unmyelinated axons (i.e., C-fibers), most modeling efforts focused on myelinated axons. We implemented the single-compartment model of vagal afferents from Schild et al. 1994 and extended the model into a multi-compartment axon, presenting the first cable model of a C-fiber vagal afferent. We also implemented the updated parameters from Schild and Kunze 1997. We compared the responses of these novel models to three published models of unmyelinated axons (Rattay and Aberham 1993; Sundt et al. 2015; Tigerholm et al. 2014) and to experimental data from single fiber recordings. Comparing Schild et al. 1994 and 1997 revealed that differences in rest potential and action potential shape were driven by changes in maximum conductances rather than changes in sodium channel dynamics. Comparing the five model axons, the conduction speeds and strength-duration responses were largely within expected ranges, but none of the models captured the experimental threshold recovery cycle-including a complete absence of late subnormality in the models-and their action potential shapes varied dramatically. The Tigerholm et al. 2014 model best reproduced the experimental data, but these modeling efforts make clear that additional data are needed to parameterize and validate future models of autonomic C-fibers.

scholarly journals PROPERTIES OF DORSAL ROOT UNMEDULLATED FIBERS ON THE TWO SIDES OF THE GANGLION

1955 ◽  
Vol 38 (5) ◽  
pp. 709-728 ◽  
Author(s):  
Herbert S. Gasser
Keyword(s):  
Electron Microscope ◽  
Action Potential ◽  
Action Potentials ◽  
Dorsal Root ◽  
Compound Action Potential ◽  
Nerve Fibers ◽  
Physiological Properties ◽  
Cells Of Origin ◽  
Biophysical Mechanism ◽  
Striking Change

As an aid in the interpretation of the physiological properties of unmedullated nerve fibers, particularly those having their cells of origin in the dorsal root ganglia, more precise information about their morphology has been acquired through employment of the electron microscope. The appearance of the fibers in the skin nerves is described, with special reference to the structure of their sheaths; and a notation is made about the bearing of the axon-sheath relationship on the biophysical mechanism of conduction (p. 714). There is no basic difference between the sheath systems of the d.r.C and the s.C fibers. Attention is called to a point of similarity between the sheaths of unmyelinated and myelinated axons (p. 715). An assessment was made of the likelihood of interaction between the fibers. In action potentials showing temporal dispersion at several distances, the elevations appeared in their calculated positions. A model of a group of Schwann sheaths was constructed from successive electron microscope sections, showing that the lengths of the sheath branches are short in comparison with the wave lengths of the action potentials. Supported by these and other considerations, the argument is strongly in favor of the conclusion that among d.r.C fibers, as in other fibers, there is no cross-excitation between the axons. A new analysis of the size distribution of the fibers in a sural nerve was made from electron microscope pictures; and from the measurements the action potential was constructed. The result confirmed the view, previously expressed, that the velocities of conduction in the fibers can be precisely accounted for by multiplying the diameters by a constant. In the dorsal roots, the striking change that takes place in the appearance of the fibers and their disposition in the Schwann sheaths can be seen in Fig. 11. The axons partake of the special properties of the peripheral branches, which necessitated the creation of the subdivision of d.r.C fibers. But, their diameters are much smaller. At a set of reduced conduction velocities the configuration of the compound action potential in the nerves is repeated in the roots, with the root velocities still conforming to the size-velocity rule derived from nerve axons.

Axotomy Increases the Excitability of Dorsal Root Ganglion Cells With Unmyelinated Axons

1997 ◽  
Vol 78 (5) ◽  
pp. 2790-2794 ◽  
Author(s):  
Jun-Ming Zhang ◽  
David F. Donnelly ◽  
Xue-Jun Song ◽  
Robert H. Lamotte
Keyword(s):  
Dorsal Root Ganglion ◽  
Action Potential ◽  
Dorsal Root ◽  
Ganglion Cells ◽  
Nerve Fibers ◽  
Resting Membrane Potential ◽  
C Cells ◽  
Fast Blue ◽  
Unmyelinated Axons ◽  
Dorsal Root Ganglion Cells

Zhang, Jun-Ming, David F. Donnelly, Xue-Jun Song, and Robert H. LaMotte. Axotomy increases the excitability of dorsal root ganglion cells with unmyelinated axons. J. Neurophysiol. 78: 2790–2794, 1997. To better understand the neuronal mechanism of neuropathic pain, the effect of axotomy on the excitability of dorsal root ganglion (DRG) cells with unmyelinated axons (C cells) was investigated. Whole cell patch-clamp recordings were performed on intact DRG cells with intact axons or with axons transected 7–12 days earlier. C cells were identified by 1) soma size, 2) action potential morphology, 3) conduction velocity, and 4) in some cases, injection of Fast Blue into the injured nerve fibers. Axotomy reduced (more negative) action potential threshold but did not significantly change resting membrane potential, action potential duration, or maximal depolarization rate. Axotomy significantly increased the peak sodium current measured under voltage-clamp conditions. In Fast Blue–labeled (injured) cells, thetetrodotoxin (TTX)-sensitive current was enhanced while the TTX-resistant current was reduced. These results suggest that axotomy increased the excitability of C cells, possibly because of a preferential increase in expression of TTX-sensitive sodium currents.

scholarly journals P2X2 receptors differentiate placodal vs. neural crest C-fiber phenotypes innervating guinea pig lungs and esophagus

2008 ◽  
Vol 295 (5) ◽  
pp. L858-L865 ◽  
Author(s):  
Kevin Kwong ◽  
Marian Kollarik ◽  
Christina Nassenstein ◽  
Fei Ru ◽  
Bradley J. Undem
Keyword(s):  
Guinea Pig ◽  
Neural Crest ◽  
Single Cell ◽  
Dorsal Root Ganglia ◽  
Dorsal Root ◽  
Receptor Activation ◽  
Rt Pcr ◽  
C Fibers ◽  
Embryonic Origin ◽  
Ganglion Neurons

The lungs and esophagus are innervated by sensory neurons with somata in the nodose, jugular, and dorsal root ganglion. These sensory ganglia are derived from embryonic placode (nodose) and neural crest tissues (jugular and dorsal root ganglia; DRG). We addressed the hypothesis that the neuron's embryonic origin (e.g., placode vs. neural crest) plays a greater role in determining particular aspects of its phenotype than the environment in which it innervates (e.g., lungs vs. esophagus). This hypothesis was tested using a combination of extracellular and patch-clamp electrophysiology and single-cell RT-PCR from guinea pig neurons. Nodose, but not jugular C-fibers innervating the lungs and esophagus, responded to α,β-methylene ATP with action potential discharge that was sensitive to the P2X3 (P2X2/3) selective receptor antagonist A-317491. The somata of lung- and esophagus-specific sensory fibers were identified using retrograde tracing with a fluorescent dye. Esophageal- and lung-traced neurons from placodal tissue (nodose neurons) responded similarly to α,β-methylene ATP (30 μM) with a large sustained inward current, whereas in neurons derived from neural crest tissue (jugular and DRG neurons), the same dose of α,β-methylene ATP resulted in only a transient rapidly inactivating current or no detectable current. It has been shown previously that only activation of P2X2/3 heteromeric receptors produce sustained currents, whereas homomeric P2X3 receptor activation produces a rapidly inactivating current. Consistent with this, single-cell RT-PCR analysis revealed that the nodose ganglion neurons innervating the lungs and esophagus expressed mRNA for P2X2 and P2X3 subunits, whereas the vast majority of jugular and dorsal root ganglia innervating these tissues expressed only P2X3 mRNA with little to no P2X2 mRNA expression. We conclude that the responsiveness of C-fibers innervating the lungs and esophagus to ATP and other purinergic agonists is determined more by their embryonic origin than by the environment of the tissue they ultimately innervate.

scholarly journals The Effect of Trematode Parasites on the Growth of Littorina Neritoides (L.)

1941 ◽  
Vol 25 (1) ◽  
pp. 69-80 ◽  
Author(s):  
Miriam Rothschild
Keyword(s):  
Intermediate Host ◽  
Large Size ◽  
Size Groups ◽  
Second Intermediate Host ◽  
Upward Slope ◽  
Accelerated Growth ◽  
The Difference ◽  
First Intermediate Host ◽  
Low Rate ◽  
Trematode Parasites

If the number of infections with (a) trematode parthenitae and cercariae using Littorina neritoides as first intermediate host only, and (b) encysted metacercariae using L. neritoides as second intermediate host only, are plotted against the size of the snails, two different curves result. The first shows a low rate of infection in the small size groups, but a steep upward slope rising to 91% in the large size groups. The second shows a curve increasing uniformly to 87% infection.Possible interpretations are discussed, and it is concluded that the difference is probably due to the fact that primary infections cause accelerated growth in the host.

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.

Functional changes in dorsal root ganglion cells after chronic nerve constriction in the rat

1995 ◽  
Vol 73 (5) ◽  
pp. 1811-1820 ◽  
Author(s):  
Y. Xie ◽  
J. Zhang ◽  
M. Petersen ◽  
R. H. LaMotte
Keyword(s):  
Dorsal Root Ganglion ◽  
Dorsal Root ◽  
Ganglion Cells ◽  
Threshold Concentration ◽  
Injury Site ◽  
Functional Changes ◽  
C Fibers ◽  
Excitatory Responses ◽  
Dorsal Root Ganglion Cells ◽  
Thermal Stimuli

1. We studied the effects of a chronic nerve constriction on the evoked responses in dorsal root fibers in the rat to norepinephrine and to thermal stimuli applied either to the dorsal root ganglion (DRG) or the site of nerve injury. We recorded a total of 59 C fibers, 15 A delta-fibers, and 46 A beta-fibers from the L5 dorsal root of the rats 11-52 days after a loose ligation of the ipsilateral sciatic nerve. Most fibers were identified by the presence of spontaneous activity (SA) that originated partially at and/or proximal to the injury site. In addition, we recorded 20 C fibers, 1 A delta-fiber, and 28 A beta-fibers from the dorsal roots of normal, uninjured neurons. 2. In nerve-injured rats, the SA of some C fibers was generally increased by cooling and decreased by heating either site. In contrast, the SA of most A beta-fibers was increased by heating either the injury site or the DRG. Cooling the DRG decreased SA in A beta-fibers, whereas cooling the injury site typically had no effect. Excitatory responses were not evoked in any fiber group when the same thermal stimuli were applied to the nerve or DRG tested in normal, uninjured rats. 3. Norepinephrine (< 0.5 mM) applied either to the injury site or the DRG increased the SA of most C fibers and A delta-fibers but only a minority of A beta-fibers in previously injured nerves. The threshold concentration for excitation of the DRG somata of C fibers was 0.01 mM. No effects were found for fibers in uninjured nerves. 4. The effect of norepinephrine was blocked by a pretreatment with yohimbine, an alpha 2-blocker, but not with prazosin, an alpha 1-blocker. 5. Stimulation of the sympathetic trunk (L2-L3) excited most C fibers and a minority of A beta-fibers. In contrast, the SA of a minority of C fibers and A beta-fibers was depressed during sympathetic stimulation. 6. After a chronic nerve constriction the DRG becomes a source of abnormal activity modulated by sympathetically released norepinephrine acting on alpha 2 receptors in DRG somata. This neuropathic activity may contribute to cutaneous pain and hyperalgesia.

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