scholarly journals Sodium influxes in internally perfused squid giant axon during voltage clamp

1969 ◽  
Vol 201 (3) ◽  
pp. 657-664 ◽  
Author(s):  
I. Atwater ◽  
F. Bezanilla ◽  
E. Rojas
Keyword(s):  
Voltage Clamp ◽  
Giant Axon ◽  
Squid Giant Axon

The effect of displacement current on the measurement of reversal potential in squid giant axon

1982 ◽  
Vol 60 (12) ◽  
pp. 1541-1544 ◽  
Author(s):  
H. Wodlinger ◽  
H. Kunov ◽  
H. L. Atwood
Keyword(s):  
Voltage Clamp ◽  
Time Constant ◽  
Reversal Potential ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Displacement Current ◽  
Before And After

The measurement of the sodium reversal potential (Erev), as that potential where the early current reverses during voltage clamp, was found to exceed the true Erev by 4.1 ± 2.4 mV (mean ± SD) in squid giant axon. This error was found in both intact and internally perfused axons and is due to interference from the displacement current. This was shown by subtraction of the current records obtained before and after treatment with tetrodotoxin (TTX). The error in Erev is proportional to [Formula: see text] where Td is the time constant of the displacement current.

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

1970 ◽  
Vol 207 (1) ◽  
pp. 151-164 ◽  
Author(s):  
Francisco Bezanilla ◽  
Eduardo Rojas ◽  
Robert E. Taylor
Keyword(s):  
Voltage Clamp ◽  
Time Course ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Sodium Influx

scholarly journals THE EFFECT OF SODIUM AND POTASSIUM IONS ON THE IMPEDANCE CHANGE ACCOMPANYING THE SPIKE IN THE SQUID GIANT AXON

1953 ◽  
Vol 37 (1) ◽  
pp. 25-37 ◽  
Author(s):  
Harry Grundfest ◽  
Abraham M. Shanes ◽  
Walter Freygang
Keyword(s):  
Voltage Clamp ◽  
Potassium Level ◽  
Giant Axon ◽  
Sodium Concentration ◽  
Squid Giant Axon ◽  
Potassium Ions ◽  
Impedance Change ◽  
Voltage Clamp Technique ◽  
Sodium And Potassium ◽  
Identical Fashion

Decrease of the sodium concentration of the medium depresses both the spike and the associated impedance change in almost identical fashion. Elevation of the potassium level also depresses both phenomena, but affects the impedance change more than the spike; it slows the return to the initial impedance level. The effects on the threshold to brief square waves are also described. These results appear largely accounted for by the observations of Hodgkin and Huxley with the voltage clamp technique and by their recent hypothesis as to nature of the spike processes.

scholarly journals Ammonium Ion Currents in the Squid Giant Axon

1969 ◽  
Vol 53 (3) ◽  
pp. 342-361 ◽  
Author(s):  
Leonard Binstock ◽  
Harold Lecar
Keyword(s):  
Voltage Clamp ◽  
Ammonium Chloride ◽  
Time Course ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Ammonium Ion ◽  
Ion Currents ◽  
Potassium Permeability ◽  
Nerve Excitability ◽  
Conductance Changes

Voltage-clamp studies on intact and internally perfused squid giant axons demonstrate that ammonium can substitute partially for either sodium or potassium. Ammonium carries the early transient current with 0.3 times the permeability of sodium and it carries the delayed current with 0.3 times the potassium permeability. The conductance changes observed in voltage clamp show approximately the same time course in ammonium solutions as in the normal physiological solutions. These ammonium ion permeabilities account for the known effects of ammonium on nerve excitability. Experiments with the drugs tetrodotoxin (TTX) and tetraethyl ammonium chloride (TEA) demonstrate that these molecules block the early and late components of the current selectively, even when both components are carried by the same ion, ammonium.

Nonuniform Response in the Squid Axon Membrane Under ‘Voltage-Clamp’

1958 ◽  
Vol 193 (2) ◽  
pp. 309-317 ◽  
Author(s):  
I. Tasaki ◽  
C. S. Spyropoulos
Keyword(s):  
Voltage Clamp ◽  
Giant Axon ◽  
Membrane Depolarization ◽  
Squid Giant Axon ◽  
Membrane Currents ◽  
Active Area ◽  
Squid Axon ◽  
Axon Membrane ◽  
Spatial Nonuniformity ◽  
Main Portion

By cooling a portion of the squid giant axon at a time, it was shown that the repetitive membrane currents observed under the so-called voltage-clamp conditions derived from the main portion of the ‘clamped’ axon membrane and not from the lateral unclamped portion. An improvement of the guard system by the use of the method of ‘double voltage-clamp’ also supported this conclusion. Using a microelectrode introduced through the axon surface, it was found that, when the clamping level was between 20 and 35 mv, some part of the membrane became fully active while other parts remained at rest. In this range of membrane depolarization, the active area was found to increase with increasing depolarization. It was stressed that spatial nonuniformity of the squid axon membrane has to be taken into consideration in the interpretation of the results of so-called voltage-clamp experiments.

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