On the slowly rising phase of the sodium gating current in the squid giant axon

High-resolution records of the sodium gating current in the squid giant axon demonstrate the existence of a slowly rising phase that is first apparent at pulse potentials slightly below zero, and becomes increasingly pronounced at more positive potentials. At +80 mV the current reaches its peak with...

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Veröffentlicht in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 1998-02, Vol.265 (1393), p.255-262
Hauptverfasser: Keynes, R.D., Elinder, F.
Format: Artikel
Sprache:eng
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Zusammenfassung:High-resolution records of the sodium gating current in the squid giant axon demonstrate the existence of a slowly rising phase that is first apparent at pulse potentials slightly below zero, and becomes increasingly pronounced at more positive potentials. At +80 mV the current reaches its peak with a delay of 30 μs at 10°C. It is suggested that this current is generated by the first two steps labelled R ←P and P ←A in the S4 units of all four domains of the series-parallel gating system, activating the channel before its opening by the third steps A ←B in domains I, II and III in conjunction with hydration. The kinetics of the slowly rising phase can only be explained by the incorporation of an appropriate degree of voltage-dependent cooperativity between the S4 voltage-sensors for their two initial transitions.
ISSN:0962-8452
1471-2954
1471-2954
DOI:10.1098/rspb.1998.0290