Changes in myelinated nerve fibres caused by insulating layers

Area of Science:

• Neuroscience
• Cell Biology
• Electrophysiology

Background:

• Myelinated nerve fibers are crucial for rapid signal transmission in the nervous system.
• Understanding the integrity of the axoplasm during experimental procedures is vital for accurate electrophysiological studies.

Purpose of the Study:

• To assess the impact of experimental sealing methods (vaseline vs. air gap) on the axoplasm of single myelinated nerve fibers.
• To evaluate the electrophysiological stability of nerve internodes under different sealing conditions.

Main Methods:

• Electron microscopy was used to examine structural changes in dissected nerve internodes.
• Electrophysiological recordings were performed to measure axoplasmic resistance over time.
• Comparison of vaseline seals and air gaps as methods for isolating nerve internodes.

Main Results:

• Vaseline seals caused a minor reduction (approx. 3x) in axoplasmic cross-sectional area, while air gaps caused a larger reduction (approx. 5x).
• Vaseline seals maintained stable axoplasmic resistance for up to 2 hours.
• Air gaps led to a rapid, humidity-dependent increase in axoplasmic resistance, doubling within ~49 minutes and increasing up to 3000-fold.

Conclusions:

• Vaseline seals offer superior stability for maintaining axoplasmic integrity and resistance in nerve fiber experiments compared to air gaps.
• Air gaps introduce significant experimental variability due to rapid changes in axoplasmic resistance, influenced by atmospheric humidity.
• Findings provide critical insights for optimizing voltage-clamp experiments on myelinated nerve fibers.