scholarly journals Sodium channel selectivity. Dependence on internal permeant ion concentration.

1976 ◽  
Vol 68 (2) ◽  
pp. 111-125 ◽  
Author(s):  
M Cahalan ◽  
T Begenisich
Keyword(s):  
Sodium Channel ◽  
Ion Concentration ◽  
Selectivity Ratio ◽  
Squid Axon ◽  
Perfusion Medium ◽  
Chloride Permeability ◽  
Channel Selectivity ◽  
Sucrose Solutions ◽  
Internal Concentration ◽  
Reversal Potentials

The selectivity of sodium channels in squid axon membranes was investigated with widely varying concentrations of internal ions. The selectivity ratio, PNa/PK, determined from reversal potentials decreases from 12.8 to 5.7 to 3.5 as the concentration of internal potassium is reduced from 530 to 180 to 50 mM, respectively. The internal KF perfusion medium can be diluted by tetramethylammonium (TMA), Tris, or sucrose solutions with the same decrease in PNa/PK. The changes in the selectivity ratio depend upon internal permeant ion concentration rather than ionic strength, membrane potential, or chloride permeability. Lowering the internal concentration of cesium, rubidium, guanidnium, or ammonium also reduces PNa/Pion. The selective sequence of the sodium channel is: Na greater than guanidinium greater than ammonium greater than K greater than Rb greater than Cs.

The sodium channel of excitable and non-excitable cells

1988 ◽  
Vol 21 (1) ◽  
pp. 99-128 ◽  
Author(s):  
R. Villegas ◽  
Gloria M. Villegas ◽  
J. M. Rodriguez-Grille ◽  
F. Sorais-Landaez
Keyword(s):  
Sodium Channel ◽  
Na Channel ◽  
Electrochemical Gradient ◽  
Squid Axon ◽  
Excitable Cells ◽  
Selective Increase

Excitation and conduction in the majority of excitable cells, as originally described in the squid axon, are initiated by a transient and highly selective increase of the membrane Na conductance, which allows this ion to move passively down its electrochemical gradient (Hodgkin & Katz, 1949; Hodgkin & Huxley, 1952). The term ‘Na channel’ was introduced to describe the mechanism involved in this conductance change (Hodgkin & Keynes, 1955).

scholarly journals Analysis of sodium current fluctuations in the cut-open squid giant axon.

1984 ◽  
Vol 83 (2) ◽  
pp. 133-142 ◽  
Author(s):  
I Llano ◽  
F Bezanilla
Keyword(s):  
Sodium Channel ◽  
Sodium Channels ◽  
Sodium Current ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Statistical Techniques ◽  
Current Fluctuations ◽  
Small Populations ◽  
Squid Axon ◽  
Single Sodium Channel

Patch pipettes were used to record the current arising from small populations of sodium channels in voltage-clamped cut-open squid axons. The current fluctuations associated with the time-variant sodium conductance were analyzed with nonstationary statistical techniques in order to obtain an estimate for the conductance of a single sodium channel. The results presented support the notion that the open sodium channel in the squid axon has only one value of conductance, 3.5 pS.

Ion Selectivity Strategies of Sodium Channel Selectivity Filters

2014 ◽  
Vol 47 (12) ◽  
pp. 3580-3587 ◽  
Author(s):  
Todor Dudev ◽  
Carmay Lim
Keyword(s):  
Sodium Channel ◽  
Ion Selectivity ◽  
Channel Selectivity

scholarly journals Bases of Sodium Channel Selectivity Among Organic Cations

2016 ◽  
Vol 110 (3) ◽  
pp. 322a
Author(s):  
Yibo Wang ◽  
Rocio K. Finol-Urdaneta ◽  
Sergei Yu Noskov ◽  
Robert J. French
Keyword(s):  
Sodium Channel ◽  
Organic Cations ◽  
Channel Selectivity

The effect of sugars on the respiratory response of beech mycorrhizas to salts

1958 ◽  
Vol 148 (932) ◽  
pp. 403-418 ◽  
Keyword(s):  
Sucrose Solution ◽  
High Energy ◽  
Respiratory Response ◽  
Factors Affecting ◽  
Sugar Absorption ◽  
Rapid Release ◽  
Sucrose Solutions ◽  
Internal Concentration ◽  
Rate Of Absorption ◽  
Respiratory Stimulation

Beech mycorrhizas are shown to be capable of absorbing sugar from solutions of glucose, fructose or sucrose. The rate of absorption of hexoses is shown to be dependent upon the concentration applied, upon the pH of the medium, and to be sensitive to the presence of 2:4-dinitrophenol and silver nitrate. Glucose is preferentially absorbed from mixtures of glucose and fructose. Mycorrhizas immersed in sucrose solution cause a rapid release of hexoses into the medium, fructose being released in greater quantity than glucose. From a study of the factors affecting sugar absorption from sucrose solutions it is concluded that sucrose itself is not absorbed, but that the glucose moiety is preferentially selected for absorption. The release of hexoses is little affected by heat treatment of the plant tissue which abolishes its ability to absorb sugar. As hexoses are absorbed, sucrose and polysaccharides increase in the tissues, but the change in the internal concentration of hexoses is small. During sugar absorption a respiratory stimulation occurs which is similar to the respiratory rise occurring during the absorption of nutrient salts. It is suggested from a study of the combined effects of phosphate and sugars that these respiratory effects of sugars and salts may have a common explanation if it is assumed that consumption of high energy phosphate occurs in both processes. This hypothesis is discussed.

scholarly journals Modified kinetics and selectivity of sodium channels in frog skeletal muscle fibers treated with aconitine.

1982 ◽  
Vol 80 (5) ◽  
pp. 713-731 ◽  
Author(s):  
D T Campbell
Keyword(s):  
Skeletal Muscle ◽  
Sodium Channel ◽  
Sodium Channels ◽  
State Level ◽  
Steady State Level ◽  
Channel Block ◽  
Frog Skeletal Muscle ◽  
Channel Kinetics ◽  
Ionic Selectivity ◽  
Channel Selectivity

The effect of the plant alkaloid aconitine on sodium channel kinetics, ionic selectivity, and blockage by protons and tetrodotoxin (TTX) has been studied in frog skeletal muscle. Treatment with 0.25 or 0.3 mM aconitine alters sodium channels so that the threshold of activation is shifted 40-50 mV in the hyperpolarized direction. In contrast to previous results in frog nerve, inactivation is complete for depolarizations beyond about -60 mV. After aconitine treatment, the steady state level of inactivation is shifted approximately 20 mV in the hyperpolarizing direction. Concomitant with changes in channel kinetics, the relative permeability of the sodium channel to NH4,K, and Cs is increased. This altered selectivity is not accompanied by altered block by protons or TTX. The results suggest that sites other than those involved in channel block by protons and TTX are important in determining sodium channel selectivity.

scholarly journals Ultraviolet-Induced Sensitivity to Visible Light in Ultraviolet Receptors of Limulus

1972 ◽  
Vol 59 (2) ◽  
pp. 186-200 ◽  
Author(s):  
John Nolte ◽  
Joel E. Brown
Keyword(s):  
Spectral Sensitivity ◽  
Electrical Response ◽  
Receptor Potential ◽  
Ion Concentration ◽  
Sensitivity Curve ◽  
Long Wavelength ◽  
Median Ocellus ◽  
Wavelength Light ◽  
Reversal Potentials ◽  
Spectral Sensitivity Curve

In the UV-sensitive photoreceptors of the median ocellus (UV cells), prolonged depolarizing afterpotentials are seen following a bright UV stimulus. These afterpotentials are abolished by long-wavelength light. During a bright UV stimulus, long-wavelength light elicits a sustained negative-going response. These responses to long-wavelength light are called repolarizing responses. The spectral sensitivity curve for the repolarizing responses peaks at 480 nm; it is the only spectral sensitivity curve for a median ocellus electrical response known to peak at 480 nm. The reversal potentials of the repolarizing response and the depolarizing receptor potential are the same, and change in the same way when the external sodium ion concentration is reduced. We propose that the generation of repolarizing responses involves a thermally stable intermediate of the UV-sensitive photopigment of UV cells.

scholarly journals Release of proteins from the inner surface of squid axon membrane labeled with tritiated N-ethylmaleimide.

1976 ◽  
Vol 68 (4) ◽  
pp. 385-395 ◽  
Author(s):  
I Inoue ◽  
H C Pant ◽  
I Tasaki ◽  
H Gainer
Keyword(s):  
Membrane Surface ◽  
Protein Release ◽  
Squid Axon ◽  
Perfusion Medium ◽  
Intracellular Perfusion ◽  
Covalent Bonds ◽  
Axon Membrane ◽  
Inner Surface ◽  
Axonal Excitability ◽  
External Calcium

Proteins in the inner surface of the squid axon membrane were labeled by intracellular perfusion of [3H]N-ethylmaleimide (NEM), which forms covalent bonds with free sulfhydryl groups. The excitability of the axon was unaffected by the [3H]NEM perfusion. After washout of the unbound label, the perfusate was monitored for the release of labeled proteins. Labeled proteins were released from the inner membrane surface by potassium depolarization of the axon only in the presence of external calcium ions. Replacement of the fluoride ion in the perfusion medium by various anions also caused labeled protein release. The order of effectiveness was SCN- greater than Br- greater than Cl- greater than F-. The extent of labeled protein release by the various anions was correlated with their effects on axonal excitability. The significance of these results is discussed.

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