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Aplysia giant cell: soma-axon voltage clamp current differences.
Science (New York, N.Y.)
|November 23, 1973
Summary
Local membrane currents were studied in neuron somas. Tetrodotoxin (TTX) revealed that early inward currents primarily flow through the axon and nearby soma, while later currents are larger across the somatic membrane.
Area of Science:
- Neuroscience
- Cellular Electrophysiology
Background:
- Understanding the spatial distribution of ion channel activity is crucial for comprehending neuronal excitability.
- The soma and axon initial segment are key regions for action potential initiation and propagation.
Purpose of the Study:
- To investigate the localization of early and late membrane currents in different regions of the neuronal soma.
- To determine the effect of tetrodotoxin (TTX) on the spatial distribution of these currents.
Main Methods:
- Voltage clamp recordings were performed on various regions of the soma.
- Local membrane currents were measured in normal bathing medium and after the addition of 10(-5) M tetrodotoxin (TTX).
Main Results:
- In normal media, the early inward current was predominantly observed in the axon and the soma membrane adjacent to the axon.
- Upon addition of TTX, a significant inward current was detected in the somatic membrane further away from the axon.
- Late currents showed increased amplitude at the soma in both normal and TTX-treated conditions.
Conclusions:
- The early inward current is primarily mediated by TTX-sensitive sodium channels located in the axon and peri-axonal soma.
- TTX-resistant currents contribute significantly to the late somatic membrane currents.
- These findings highlight the distinct spatial segregation of different ionic currents within the neuron.