Sodium channel inactivation in the crayfish giant axon. Must channels open before inactivating
Experiments on sodium channel inactivation kinetics were performed on voltage-clamped crayfish giant axons. The primary goals was to investigate whether channels must open before activating. Voltage-clamp artifacts were minimized by the use of low-sodium solutions and full series resistance compensation, and the spatial uniformity of the currents was checked with a closely spaced pair of electrodes used to measure local current densities. For membrane potentials between -40 and +40 mV, sodium currents decay to zero with a single exponential time-course. The time constant for decay is a steep function of membrane potential. The time-course of inactivation measured with the double-pulse method is very similar to the decay of current at the same potential. Steady-state inactivation curves measured with different test pulses are identical. The time-course of doubling pulse inactivation shows a lag that roughly correlates with the opening of sodium channels, but it is not strictly necessary for channels to open before inactivating. Measurements of the potential dependence of the integral of sodium conductance are also inconsistent with the simplest cases of models in which channels must open before activating.
- Research Organization:
- Univ. of Rochester Medical Center, New York
- OSTI ID:
- 5953006
- Journal Information:
- Biophys. J.; (United States), Vol. 35:3
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CELL MEMBRANES
ELECTRIC POTENTIAL
SODIUM COMPOUNDS
MEMBRANE TRANSPORT
BIOLOGICAL MODELS
CATIONS
CHEMICAL ACTIVATION
CRUSTACEANS
INACTIVATION
ION CHANNELING
KINETICS
ALKALI METAL COMPOUNDS
ANIMALS
AQUATIC ORGANISMS
ARTHROPODS
CELL CONSTITUENTS
CHANNELING
CHARGED PARTICLES
INVERTEBRATES
IONS
MEMBRANES
550200* - Biochemistry