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Late sodium current in the node of Ranvier
Pflugers Archiv : European Journal of Physiology
|January 1, 1975
Summary
A small fraction of sodium channels in frog nerve fibers fail to inactivate during prolonged depolarization. This results in a late sodium current, particularly noticeable in sensory nerve fibers.
Area of Science:
- Neuroscience
- Cellular Electrophysiology
Background:
- Sodium channels are crucial for nerve impulse propagation.
- Channel inactivation is a key mechanism for regulating neuronal excitability.
Purpose of the Study:
- To investigate the behavior of sodium channels during prolonged depolarizing pulses in myelinated nerve fibers.
- To identify any non-inactivating sodium currents and their characteristics.
Main Methods:
- Voltage clamp experiments were performed on nodes of Ranvier in myelinated nerve fibers of Rana esculenta.
- Analysis of sodium currents during long-lasting depolarizing pulses.
Main Results:
- A small fraction of sodium channels demonstrated a failure to inactivate.
- A small, late sodium current was observed, superimposed on leakage and potassium currents.
- This late sodium current was more pronounced in sensory fibers compared to motor fibers.
Conclusions:
- Some sodium channels exhibit incomplete inactivation, contributing to persistent inward currents.
- The presence of a late sodium current may influence the excitability differences between sensory and motor nerve fibers.