scholarly journals Long-lasting increase in axonal excitability after epidurally applied DC

2017 ◽  
Vol 118 (2) ◽  
pp. 1210-1220 ◽  
Author(s):  
Elzbieta Jankowska ◽  
Dominik Kaczmarek ◽  
Francesco Bolzoni ◽  
Ingela Hammar
Keyword(s):  
Pain Control ◽  
Time Course ◽  
Nerve Fibers ◽  
Myelinated Nerve ◽  
Epidural Stimulation ◽  
Myelinated Nerve Fibers ◽  
Dorsal Columns ◽  
New Form ◽  
Axonal Excitability ◽  
Dc Polarization

The study indicates a new form of plasticity of myelinated fibers. The differences in time course of DC-evoked increases in the excitability of myelinated nerve fibers in the dorsal columns and in preterminal axonal branches suggest that distinct mechanisms are involved in them. The results show that combining epidural stimulation and transspinal DC polarization may dramatically improve their outcome and result in more effective pain control and the return of impaired motor functions.

scholarly journals Long-term effects of direct current are reproduced by intermittent depolarization of myelinated nerve fibers

2018 ◽  
Vol 120 (3) ◽  
pp. 1173-1185 ◽  
Author(s):  
M. Bączyk ◽  
E. Jankowska
Keyword(s):  
Nerve Fibers ◽  
Field Potentials ◽  
Applied Current ◽  
Myelinated Nerve ◽  
Myelinated Nerve Fibers ◽  
Current Pulses ◽  
Afferent Fibers ◽  
Dorsal Columns ◽  
Stimulation Of

Direct current (DC) potently increases the excitability of myelinated afferent fibers in the dorsal columns, both during DC polarization of these fibers and during a considerable (>1 h) postpolarization period. The aim of the present study was to investigate whether similarly long-lasting changes in the excitability of myelinated nerve fibers in the dorsal columns may be evoked by field potentials following stimulation of peripheral afferents and by subthreshold epidurally applied current pulses. The experiments were performed in deeply anesthetized rats. The effects were monitored by changes in nerve volleys evoked in epidurally stimulated hindlimb afferents and in the synaptic actions of these afferents. Both were found to be facilitated during as well as following stimulation of a skin nerve and during as well as following epidurally applied current pulses of 5- to 10-ms duration. The facilitation occurring ≤2 min after skin nerve stimulation could be linked to both primary afferent depolarization and large dorsal horn field potentials, whereas the subsequent changes (up to 1 h) were attributable to effects of the field potentials. The findings lead to the conclusion that the modulation of spinal activity evoked by DC does not require long-lasting polarization and that relatively short current pulses and intrinsic field potentials may contribute to plasticity in spinal activity. These results suggest the possibility of enhancing the effects of epidural stimulation in human subjects by combining it with polarizing current pulses and peripheral afferent stimulation and not only with continuous DC. NEW & NOTEWORTHY The aim of this study was to define conditions under which a long-term increase is evoked in the excitability of myelinated nerve fibers. The results demonstrate that a potent and long-lasting increase in the excitability of afferent fibers traversing the dorsal columns may be induced by synaptically evoked intrinsic field as well as by epidurally applied intermittent current pulses. They thus provide a new means for the facilitation of the effects of epidural stimulation.

scholarly journals Branching points of primary afferent fibers are vital for the modulation of fiber excitability by epidural DC polarization and by GABA in the rat spinal cord

2020 ◽  
Vol 124 (1) ◽  
pp. 49-62
Author(s):  
Yaqing Li ◽  
Krishnapriya Hari ◽  
Ana M. Lucas-Osma ◽  
Keith K. Fenrich ◽  
David J. Bennett ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Nerve Fibers ◽  
Rat Spinal Cord ◽  
Epidural Stimulation ◽  
Afferent Fibers ◽  
Branching Points ◽  
Dorsal Columns ◽  
Primary Afferent Fibers ◽  
Sensory Fibers ◽  
Dc Polarization

Polarization of sensory fibers traversing dorsal columns of the spinal cord may considerably increase the excitability of these fibers. We show that this involves the effects of current at branching points of afferent fibers and depends on extrasynaptic of GABA. These results contribute to our understanding of the mechanism underlying plasticity of activation of nerve fibers and may be used to increase the effectiveness of epidural stimulation in humans and recovery of spinal functions.

scholarly journals THE SUBMICROSCOPIC ORGANIZATION OF AXON MATERIAL ISOLATED FROM MYELIN NERVE FIBERS

1953 ◽  
Vol 98 (3) ◽  
pp. 269-276 ◽  
Author(s):  
E. De Robertis ◽  
C. M. Franchi
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Phase Contrast ◽  
Nerve Fibers ◽  
Myelinated Nerve ◽  
Myelinated Nerve Fibers ◽  
Dense Granules ◽  
Small Clusters ◽  
Membranous Material ◽  
The Way

A technique has been developed for the extrusion of axon material from myelinated nerve fibers. This material is then compressed and prepared for observation with the electron microscope. All the stages of preparation and purification of the axon material can be checked microscopically and in the present paper they are illustrated with phase contrast photomicrographs. Observation with the electron microscope of the compressed axons showed the presence of the following components: granules, fibrils, and a membranous material. Only the larger granules could be seen with the ordinary microscope. A considerable number of dense granules were observed. Of these the largest resemble typical mitochondria of 250 mµ by 900 mµ. In addition rows or small clusters of dense granules ranging in diameter from 250 to 90 mµ were present. In several specimens fragments of a membrane 120 to 140 A thick and intimately connected with the axon were found. The entire axon appeared to be constituted of a large bundle of parallel tightly packed fibrils among which the granules are interspersed. The fibrils are of indefinite length and generally smooth. They are rather labile structures, less resistant in the rat than in the toad nerve. They varied between 100 and 400 A in diameter and in some cases disintegrated into very fine filaments (less than 100 A thick). The significance is discussed of the submicroscopic structures revealed by electron microscopy of the material prepared in the way described.

scholarly journals A simplified empirical modeling of electrophysiological activity in a bundle of myelinated nerve fibers

2016 ◽  
Vol 14 (7) ◽  
pp. 3345-3350 ◽  
Author(s):  
Alvaro Gabriel Piza ◽  
Fernando Daniel Farfan ◽  
Ana Lia Albarracin ◽  
Facundo Adrian Lucianna ◽  
Jorge Humberto Soletta ◽  
...  
Keyword(s):  
Nerve Fibers ◽  
Empirical Modeling ◽  
Myelinated Nerve ◽  
Myelinated Nerve Fibers ◽  
Electrophysiological Activity

scholarly journals Myelin Basic Protein and Cardiac Sympathetic Neurodegeneration in Nonhuman Primates

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Jeanette M. Metzger ◽  
Helen N. Matsoff ◽  
Don Vu ◽  
Alexandra D. Zinnen ◽  
Kathryn M. Jones ◽  
...  
Keyword(s):  
Left Ventricle ◽  
Myelin Basic Protein ◽  
Basic Protein ◽  
Rhesus Macaques ◽  
Sympathetic Neurons ◽  
Nerve Fibers ◽  
Myelinated Nerve ◽  
Myelinated Nerve Fibers ◽  
Pparγ Agonist ◽  
Nerve Bundles

Minimal myelination is proposed to be a contributing factor to the preferential nigral neuronal loss in Parkinson’s disease (PD). Similar to nigral dopaminergic neurons, sympathetic neurons innervating the heart have long, thin axons which are unmyelinated or minimally myelinated. Interestingly, cardiac sympathetic loss in PD is heterogeneous across the heart, yet the spatial relationship between myelination and neurodegeneration is unknown. Here, we report the mapping of myelin basic protein (MBP) expression across the left ventricle of normal rhesus macaques (n = 5) and animals intoxicated with systemic 6-OHDA (50 mg/kg iv) to model parkinsonian cardiac neurodegeneration (n = 10). A subset of 6-OHDA-treated rhesus received daily dosing of pioglitazone (5 mg/kg po; n = 5), a PPARγ agonist with neuroprotective properties. In normal animals, MBP-immunoreactivity (-ir) was identified surrounding approximately 14% of axonal fibers within nerve bundles of the left ventricle, with more myelinated nerve fibers at the base level of the left ventricle than the apex p < 0.014 . Greater MBP-ir at the base was related to a greater number of nerve bundles at that level relative to the apex p < 0.05 , as the percent of myelinated nerve fibers in bundles was not significantly different between levels of the heart. Cardiac sympathetic loss following 6-OHDA was associated with decreased MBP-ir in cardiac nerve bundles, with the percent decrease of MBP-ir greater in the apex (84.5%) than the base (52.0%). Interestingly, cardiac regions and levels with more MBP-ir in normal animals showed attenuated sympathetic loss relative to areas with less MBP-ir in 6-OHDA + placebo (r = −0.7, p < 0.014 ), but not in 6-OHDA + pioglitazone (r = −0.1) subjects. Our results demonstrate that myelination is present around a minority of left ventricle nerve bundle fibers, is heterogeneously distributed in the heart of rhesus macaques, and has a complex relationship with cardiac sympathetic neurodegeneration and neuroprotection.

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