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Multiple modes of N-type calcium channel activity distinguished by differences in gating kinetics
A H Delcour1, D Lipscombe, R W Tsien
1Department of Molecular and Cellular Physiology, Beckman Center, Stanford University Medical Center, California 94305.
Summary
N-type calcium channels in frog neurons exhibit distinct gating modes, influencing neurotransmitter release. These modes, characterized by different opening/closing kinetics and voltage dependence, suggest cellular control over channel function.
Area of Science:
- Neuroscience
- Ion Channel Physiology
- Cellular Electrophysiology
Background:
- N-type calcium channels are crucial for neurotransmitter release in many neurons.
- Understanding their gating kinetics is essential for elucidating neuronal function.
Purpose of the Study:
- To characterize the rapid opening and closing kinetics of N-type calcium channel gating.
- To identify distinct gating modes and their properties in frog sympathetic neurons.
Main Methods:
- Cell-attached patch recordings were performed using 110 mM Ba2+ as the charge carrier.
- Single N-type calcium channel gating was analyzed during depolarizing pulses to -10 mV.
Main Results:
- Single N-type calcium channels displayed three distinct gating modes (low-, medium-, and high-open probability).
- Each mode exhibited unique activation kinetics, mean open/closed durations, and voltage dependence.
- Transitions between modes were infrequent, with channels spending approximately 10 seconds in each mode.
Conclusions:
- N-type calcium channel gating is multimodal, with each mode possessing a distinct kinetic signature.
- The observed modal gating behavior and its variability suggest potential cellular regulation.
- These findings provide insights into the complex regulation of calcium influx and neurotransmitter release.