The morphological changes in unmyelinated peripheral nerve fibers exposed to low sodium and high potassium concentrations

Ho, K C; Friede, Reinhard L.; Garancis, John C.; Sato, Keith A.

doi:10.1016/0022-510x(81)90169-6

Cited by 5 publications

(4 citation statements)

References 18 publications

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“…increase in the number and size of paranodal intramyelinic vacuoles) happened within a nodal complex concomitant with repetitive action potential propagation, while internodal regions of axons remained unchanged. In another study [69], Schwann cells were shown to probably act as a buffer zone to protect axons from the influences of ionic concentration changes by maintaining a relatively constant periaxonal environment. All these indicate that intracellular and periaxonal ionic concentration changes induced by electrical stimulation may occur mainly at nodes of Ranvier adjacent to stimulating electrodes, while the myelin sheath may provide mechanisms resistant to the axonal morphologic alterations induced by this kind of ionic change.…”

Section: Discussionmentioning

confidence: 98%

“…In Agnew et al's study [35], charge-balanced biphasic pulses stimulation of 50 Hz at an intense amplitude resulted in an increase of [K + ] o and swollen axons. Ho et al's study [69] showed that extracellular environment changes alone (at an extremely low sodium and high potassium concentration) also caused swelling of axons. Another piece of evidence supporting this is the 'mass action' nerve injury mechanism [31-33, 47, 48, 55], summarized from studies of nerve stimulation using low frequency (<1 kHz) electrical pulses (usually <0.2 ms pulse width), in which the excessive activities of many neurons induced by stimulus are considered to change the composition of the extracellular environment (e.g.…”

Section: Discussionmentioning

confidence: 99%

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Post stimulus effects of high frequency biphasic electrical current on a fibre's conductibility in isolated frog nerves

Liu¹,

Zhu²,

Sheng³

et al. 2013

J. Neural Eng.

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This study indicates that HFB electrical currents lead to long lasting post stimulus reduction of a nerve's conductibility, which might relate to potential nerve injuries. A possible mechanism, focusing on changes in intracellular and periaxonal ionic concentrations, was proposed to underlie the reduction of the nerve's conductibility and potential nerve injuries. Greater caution and stimulation protocols with greater safety margins should be explored when utilizing HFB electrical current to block nerve conductions.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Post stimulus effects of high frequency biphasic electrical current on a fibre's conductibility in isolated frog nerves

Liu¹,

Zhu²,

Sheng³

et al. 2013

J. Neural Eng.

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“…The swelling of the paranodal region after repetitive activation which has been observed Ellisman, 1986, 1987; V. Lev-Ram and M. H. Ellisman, unpublished results) may be a consequence of such water entry. When frog nonmyelinating fibers are exposed to moderately high levels of extracellular potassium, swelling is seen in the Schwann cell and not in the axons (Ho et al, 1981). This could suggest a normally existing mechanism in Schwann cells which leads to swelling when extracellular potassium is elevated.…”

Section: A Provisionul Modelmentioning

confidence: 96%

Axonal activation-induced calcium transients in myelinating Schwann cells, sources, and mechanisms

Lev‐Ram

Ellisman

1995

J. Neurosci.

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We have investigated the role of myelinating glia in events associated with propagation of the action potential at nodes of Ranvier using combinations of optical and electrophysiological recording methods. Calcium transients were observed in Schwann cells by fluorescent imaging of the nodal complex of fibers loaded with the calcium-sensitive dye fluo3-AM. To follow [Ca2+]i changes associated with neuronal activity at the node of Ranvier, nerves loaded with fluo3 were imaged during axonal activation using laser-scanning confocal microscopy. To elucidate sources of [Ca2+]i transients, we tested the effects of drugs known to alter [Ca2+]i. [Ca2+]i transients in Schwann cells were observed in response to axonal activation and these were subsequently blocked by ryanodine if ryanodine was present during a previous [Ca2+]i transient. Bath applications of caffeine induced [Ca2+]i transients which could be blocked by ryanodine. These findings indicate that calcium-activated calcium release occurs in Schwann cells in response to impulse activity.

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“…Schwann cell processes have been observed to be enlarged near a nerve terminal following repetitive nerve stimulations (Heuser and Reese, 1973). When frog non-myelinated fibres are exposed to a moderately high level of external potassium, swelling is seen in the Schwann cells and not in the axons (Ho et al, 1981). Finally, as discussed below in potassium homeostasis in myelinated fibres, myelin vacuolization and splitting occur in the paranode during repetitive firing (Moran and Mateu, 1983;Wurtz and Ellisman, 1986).…”

Section: Mechanisms Of Channel-mediated Homeostasismentioning

confidence: 98%

Functions and distribution of voltage‐gated sodium and potassium channels in mammalian schwann cells

Chiu

1991

Glia

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Recent patch-clamp studies on freshly isolated mammalian Schwann cells suggest that voltage-gated sodium and potassium channels, first demonstrated in cells under culture conditions, are present in vivo. The expression of these channels, at least at the cell body region, appears to be dependent on the myelinogenic and proliferative states of the Schwann cell. Specifically, myelin elaboration is accompanied by a down regulation of functional potassium channel density at the cell body. One possibility to account for this is a progressive regionalization of ion channels on a Schwann cell during myelin formation. In adult myelinating Schwann cells, voltage-gated potassium channels appear to be localized at the paranodal region. Theoretical calculations have been made of activity-dependent potassium accumulations in various compartments of a mature myelinated nerve fibre; the largest potassium accumulation occurs not at the nodal gap but rather at the adjacent 2-4 microns length of periaxonal space at the paranodal junction. Schwann cell potassium channels at the paranode may contribute to ionic regulation during nerve activities.

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The morphological changes in unmyelinated peripheral nerve fibers exposed to low sodium and high potassium concentrations

Cited by 5 publications

References 18 publications

Post stimulus effects of high frequency biphasic electrical current on a fibre's conductibility in isolated frog nerves

Post stimulus effects of high frequency biphasic electrical current on a fibre's conductibility in isolated frog nerves

Axonal activation-induced calcium transients in myelinating Schwann cells, sources, and mechanisms

Functions and distribution of voltage‐gated sodium and potassium channels in mammalian schwann cells

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