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Functional coupling between sodium-activated potassium channels and voltage-dependent persistent sodium currents in
Izumi Takahashi1, Masami Yoshino2
1Department of Biology, Tokyo Gakugei University, Tokyo, Japan.
Journal of Neurophysiology
|August 14, 2015
Summary
Sodium-activated potassium (KNa) channels in cricket Kenyon cells are activated by sodium influx through persistent sodium channels (INaP). This coupling influences neuronal excitability and may play a role in memory formation.
Area of Science:
- Neuroscience
- Cellular Electrophysiology
- Insect Neurobiology
Background:
- Kenyon cells in the cricket mushroom body are crucial for learning and memory.
- Understanding the ionic mechanisms governing Kenyon cell excitability is essential for elucidating their role in cognitive functions.
Purpose of the Study:
- To investigate the functional coupling between sodium-activated potassium (KNa) channels and sodium (Na+) influx via voltage-dependent sodium channels in cricket Kenyon cells.
- To determine the specific role of persistent sodium currents (INaP) in activating KNa channels.
Main Methods:
- Single-channel KNa activity recorded using cell-attached patch configuration.
- KNa channel open probability (Po) assessed under varying Na+ concentrations and with specific channel blockers.
- Perforated whole-cell clamp analysis to measure sustained outward currents.
Main Results:
- KNa channel Po increased with Na+ concentration and decreased with Li+ substitution.
- High concentrations of TTX and riluzole, along with low Cd2+, reduced KNa channel Po, implicating persistent Na+ channels (INaP).
- Sustained outward currents dependent on Na+ influx were observed, confirming functional coupling.
Conclusions:
- KNa channels in Kenyon cells are activated by Na+ influx through voltage-dependent persistent Na+ channels (INaP).
- This functional coupling mechanism is significant for regulating Kenyon cell membrane excitability.
- The findings suggest a potential role for this coupling in the neural basis of long-term memory formation.
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