Time course of the sodium permeability change during a single membrane action potential.

1. A method for measuring the time course of ionic fluxes during a non-propagated membrane action potential is described; the technique combines intracellular perfusion of the squid giant axon with radioactive tracer methods and with a method for controlling the membrane potential during small time intervals.2.

Nerve membrane excitation without threshold.

Evidence is presented to show that for a squid axon membrane the potential response, V, is a smoothly continuous function of a stimulating current, I. This makes it unlikely that an all-or-none or sharp transition phenomenon is a major factor in the processes by which ions cross the normal squid axon membrane and, probably, other excitable membranes. Spatially uniform V and I were first produced in the squid axon with internal and external electrode arrangements and later by isolating a short length of axon between external pools of sucrose.

Time course of the sodium influx in squid giant axon during a single voltage clamp pulse.

1. Sodium influx measurements were carried out on internally perfused squid giant axons under conditions of membrane potential control.2.

Analysis of the effects of calcium or magnesium on voltage-clamp currents in perfused squid axons bathed in solutions of high potassium.

Isolated axons from the squid, Dosidicus gigas, were internally perfused with potassium fluoride solutions. Membrane currents were measured following step changes of membrane potential in a voltage-clamp arrangement with external isosmotic solution changes in the order: potassium-free artificial seawater; potassium chloride; potassium chloride containing 10, 25, 40 or 50, mM calcium or magnesium; and potassium-free artificial seawater. The following results suggest that the currents measured under voltage clamp with potassium outside and inside can be separated into two components and that one of them, the predominant one, is carried through the potassium system.

Sodium influxes in internally perfused squid giant axon during voltage clamp.

1. An experimental method for measuring ionic influxes during voltage clamp in the giant axon of Dosidicus is described; the technique combines intracellular perfusion with a method for controlling membrane potential.2.