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Internodal conduction in undissected demyelinated nerve fibres
The Journal of Physiology
|December 1, 1972
Summary
A new method allows recording nerve fiber currents, revealing demyelination slows conduction but maintains saltatory transmission. Demyelination alters myelin properties, increasing internodal conduction time and causing block during repetitive stimulation due to sodium accumulation.
Area of Science:
- Neuroscience
- Cellular Biology
- Biophysics
Background:
- Nerve impulse conduction relies on the integrity of myelinated axons.
- Demyelination, a pathological process, disrupts nerve signal transmission.
- Understanding the electrophysiological changes in demyelinated fibers is crucial for neurological research.
Purpose of the Study:
- To develop a novel method for recording longitudinal currents in single nerve fibers.
- To measure internodal conduction times in normal and demyelinated rat ventral roots.
- To investigate the electrophysiological mechanisms underlying conduction slowing in demyelination.
Main Methods:
- A new technique for recording external longitudinal currents from single, undissected rat ventral root fibers.
- Identification of multiple nodes of Ranvier along a single fiber.
- Measurement of internodal conduction times and analysis of electrical properties.
Main Results:
- Normal internodal conduction time averages 19.7 ± 4.6 μsec for fibers with 0.75–1.45 mm internodal length.
- Demyelination significantly slows conduction but preserves saltatory transmission.
- Changes in internodal capacitance and resistance contribute to conduction delay, with intracellular sodium accumulation implicated in repetitive stimulation effects.
Conclusions:
- The new method enables detailed analysis of nerve fiber conduction.
- Demyelination alters passive electrical properties of myelin, impacting conduction velocity.
- Intracellular sodium accumulation explains conduction slowing and block during tetanic stimulation in demyelinated fibers.