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After potentials in nonmyelinated nerve fibers
P Jirounek1, E Chardonnens, P C Brunet
1Département de Pharmacologie, Centre Médical Universitaire, Geneva, Switzerland.
Journal of Neurophysiology
|April 1, 1991
Summary
This study investigated nerve after potentials in rabbit vagus nerves. Researchers identified distinct hyperpolarizing and depolarizing after potentials, revealing insights into potassium and calcium ion channel activity.
Area of Science:
- Neuroscience
- Electrophysiology
- Ion Channel Physiology
Background:
- Nerve impulse propagation involves complex electrical events beyond the action potential.
- Understanding after potentials is crucial for comprehending overall nerve function and excitability.
Purpose of the Study:
- To characterize the different types of after potentials following a single action potential in desheathed rabbit vagus nerves.
- To elucidate the ionic mechanisms and channel properties underlying these after potentials.
Main Methods:
- Utilized the sucrose-gap technique to record electrical activity in rabbit vagus nerve fibers.
- Applied pharmacological agents like tetraethylammonium (TEA), 4-aminopyridine (4-AP), Ba2+, and Cd2+ to probe ion channel involvement.
- Manipulated extracellular potassium concentrations to study the depolarizing after potential (DAP).
Main Results:
- Identified a fast hyperpolarizing after potential (fHAP) linked to the delayed rectifier potassium current.
- Characterized a slow hyperpolarizing after potential (sHAP) with a calcium-dependent component suggesting calcium-activated potassium channels.
- Observed a depolarizing after potential (DAP) that was calcium-dependent and inconsistent with extracellular potassium accumulation theories.
Conclusions:
- The fHAP is primarily mediated by the delayed rectifier K+ current.
- The sHAP involves both calcium-dependent and -independent components, with the former likely due to Ca2+-activated K+ channels.
- The calcium-dependent DAP's origin remains unclear, with a potential role for glial cell electrical properties.
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01:41Action Potentials
Overview
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Resting Phase:
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