Activation and Inactivation of the Sodium Channel

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Activation and Inactivation of the Sodium Channel
SIGMA-ALDRICH
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Activation And Inactivation Of The Sodium
Channel Sodium channels are characterized by
voltage-dependent activation, rapid inactivation,
and selective ion conductance. Depolarization of
the cell membrane opens the ion pore allowing
sodium to passively enter the cell down its
concentration gradient . The increase in sodium
conductance further depolarizes the membrane to
near the sodium equilibrium potential.
Inactivation of the sodium channel occurs within
milliseconds, initiating a brief refractory
period during which the membrane is not
excitable. The mechanism of inactivation has
been modeled as a hinged lid or ball and
chain, where the intracellular loop connecting
domains III and IV of the a subunit closes the
pore and prevents passage of sodium
ions. References Lehmann-Horn, F., and
Jurkat-Rott, K., Voltage-gated ion channels and
hereditary disease. Physiol. Rev., 79, 1317-1372
(1999). Catterall, W.A., From ionic currents to
molecular mechanisms the structure and function
of voltage-gated sodium channels. Neuron, 26,
13-25 (2000).