scholarly journals Properties of maintained sodium current induced by a toxin from Androctonus scorpion in frog node of Ranvier.

1987 ◽  
Vol 383 (1) ◽  
pp. 93-114 ◽  
Author(s):  
E Benoit ◽  
J M Dubois
Keyword(s):  
Sodium Current ◽  
Node Of Ranvier

scholarly journals Kinetics of intramembrane charge movement and sodium current in frog node of Ranvier.

1982 ◽  
Vol 79 (4) ◽  
pp. 571-602 ◽  
Author(s):  
J M Dubois ◽  
M F Schneider
Keyword(s):  
Time Constant ◽  
Time Course ◽  
Sodium Current ◽  
Node Of Ranvier ◽  
Charge Movement ◽  
Intramembrane Charge Movement ◽  
Time Courses ◽  
Charge Movements ◽  
Kinetics Of ◽  
Microsecond Pulse

Intramembrane charge movement (Q) and sodium current (INa) were monitored in isolated voltage-clamped frog nodes of Ranvier, ON charge movements (QON) for pulses from the holding potential (-100 mV) to potentials V less than or equal to 0 mV followed single exponential time courses, whereas two exponentials were found for pulses to V greater than or equal to 20 mV. The voltage dependence of both QON and its time constant tauON indicated that the two ON components resolved at V greater than or equal to 20 mV were also present, though not resolvable, for pulses to V less than or equal to 0 mV. OFF charge movements (QOFF) monitored at various potentials were well described by single exponentials. When QOFF was monitored at -30 or -40 mV after a 200-microsecond pulse to +20 mV and QON was monitored at the same potential using pulses directly from -100 mV, tauON/tauOFF = 2.5 +/- 0.3. At a set OFF potential (-90 to -70 mV), tauOFF first increased with increasing duration tON of the preceding pulse to a given potential (0 to +30 mV) and then decreased with further increases in tON. The declining phase of tauOFF followed a time course similar to that of the decline in QOFF with tON. For the same pulse protocol, the OFF time constant tauNa for INA also first increased with tON but then remained constant over the tON interval during which tauOFF and QOFF were declining. After 200- or 300-microsecond pulses to +20, +20, or +50 mV, tauOFF/tauNa at -70 to -90 mV was 1.2 +/- 0.1. Similar tauOFF/tauNa ratios were predicted by channel models having three identical charged gating particles that can rapidly and reversibly form an immobile dimer or trimer after independently crossing the membrane from their OFF to their ON locations.

Late sodium current in the node of Ranvier

1975 ◽  
Vol 357 (1-2) ◽  
pp. 145-148 ◽  
Author(s):  
J. M. Dubois ◽  
C. Bergman
Keyword(s):  
Sodium Current ◽  
Node Of Ranvier ◽  
Late Sodium Current

scholarly journals Kinetics of intramembrane charge movement and conductance activation of batrachotoxin-modified sodium channels in frog node of Ranvier.

1985 ◽  
Vol 86 (3) ◽  
pp. 381-394 ◽  
Author(s):  
J M Dubois ◽  
M F Schneider
Keyword(s):  
Pulse Duration ◽  
Sodium Channels ◽  
Time Course ◽  
Sodium Current ◽  
Node Of Ranvier ◽  
Charge Movement ◽  
Exponential Time ◽  
Current Activation ◽  
Time Courses ◽  
Single Exponential

Sodium current and intramembrane gating charge movement (Q) were monitored in voltage-clamped frog node of Ranvier after modification of all sodium channels by batrachotoxin (BTX). Sodium current activation followed a single-exponential time course, provided a delay was interposed between the onset of the step ON depolarization and that of the current change. The delay decreased with increased ON depolarization and, for a constant ON depolarization, increased with prehyperpolarization. ON charge movement followed a single-exponential time course with time constants tau Q,ON slightly larger than tau Na, ON. For pulses between -70 and -50 mV, tau Q,ON/tau Na,ON = 1.14 +/- 0.08. The OFF charge movement and OFF sodium current tails after a depolarizing pulse followed single-exponential time courses, with tau Q, OFF larger than tau Na, OFF. tau Q,OFF/tau Na,OFF increased with OFF voltage from 1 near -100 mV to 2 near -160 mV. At a set OFF potential (-120 mV), both tau Q,OFF and tau Na,OFF increased with ON pulse duration. The delay in INa activation and the effect of ON pulse duration on tau Q,OFF and tau Na,OFF are inconsistent with a simple two-state, single-transition model for the gating of batrachotoxin-modified sodium channels.

scholarly journals Voltage dependence of intramembrane charge movement and conductance activation of batrachotoxin-modified sodium channels in frog node of Ranvier.

1983 ◽  
Vol 81 (6) ◽  
pp. 829-844 ◽  
Author(s):  
J M Dubois ◽  
M F Schneider ◽  
B I Khodorov
Keyword(s):  
Sodium Channel ◽  
Sodium Channels ◽  
Voltage Dependence ◽  
Sodium Current ◽  
Node Of Ranvier ◽  
Charge Movement ◽  
Gating Charge ◽  
Before And After ◽  
Intramembrane Charge Movement ◽  
The Individual

Sodium current and sodium channel intramembrane gating charge movement (Q) were monitored in voltage-clamped frog node of Ranvier after modification of all sodium channels by batrachotoxin (BTX). BTX caused an approximately threefold increase in steepness of the Q vs. voltage relationship and a 50-mV negative shift in its midpoint. The maximum amount of intramembrane charge was virtually identical before and after BTX treatment. BTX treatment eliminated the charge immobilization observed in untreated nodes after relatively long depolarizing pulses and slowed the rate of OFF charge movement after a pulse. After BTX treatment, the voltage dependence of charge movement was the same as the steady-state voltage dependence of sodium conductance activation. The observations are consistent with the hypothesis that BTX induces an aggregation of the charged gating particles associated with each channel and causes them to move as a unit having approximately three times the average valence of the individual particles. Movement of this single aggregated unit would open the BTX-modified sodium channel.

Sodium current in human small intestinal interstitial cells of cajal

2001 ◽  
Vol 120 (5) ◽  
pp. A201-A201 ◽  
Author(s):  
P STREGE ◽  
A RICH ◽  
Y OU ◽  
S GIBBONS ◽  
M SARR ◽  
...  
Keyword(s):  
Interstitial Cells Of Cajal ◽  
Sodium Current ◽  
Interstitial Cells ◽  
Small Intestinal ◽  
Cells Of Cajal
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