scholarly journals Effect of Ethanol on the Sodium and Potassium Conductances of the Squid Axon Membrane

1964 ◽  
Vol 48 (2) ◽  
pp. 279-295 ◽  
Author(s):  
John W. Moore ◽  
Werner Ulbricht ◽  
Mitsuru Takata
Keyword(s):  
Time Course ◽  
Sea Water ◽  
Squid Axon ◽  
Membrane Action ◽  
Axon Membrane ◽  
Gap Technique ◽  
Potassium Conductances ◽  
Steady State Inactivation ◽  
Sucrose Gap ◽  
Sodium And Potassium

The effects of ethanol on squid giant axons were studied by means of the sucrose-gap technique. The membrane action potential height is moderately reduced and the duration sometimes shortened by ethanol in sea water. Voltage clamp experiments showed that ethanol in sea water reduced the maximum membrane conductances for sodium (g'Na) and potassium (g'K). In experiments with multiple application of ethyl alcohol to the same spot of membrane, a reduction of g'Na to 82 per cent and of g'K to 80 per cent of their value in sea water was brought about by 3 per cent ethanol (by volume) while 6 per cent caused a decrease of g'Na to 59 per cent and of g'K to 69 per cent. Ethanol has no significant effect on the steady-state inactivation of gNa (as a function of conditioning membrane potential) or on such kinetic parameters as τh or the time course of turning on gi gNa and gK. It is concluded that ethanol mainly reduces gNa and gK in the Hodgkin-Huxley terminology.

scholarly journals Ionic Conductance Changes in Lobster Axon Membrane When Lanthanum Is Substituted for Calcium

1966 ◽  
Vol 50 (2) ◽  
pp. 461-471 ◽  
Author(s):  
M. Takata ◽  
W. F. Pickard ◽  
J. Y. Lettvin ◽  
J. W. Moore
Keyword(s):  
Sea Water ◽  
Ionic Currents ◽  
Ionic Conductance ◽  
Membrane Action ◽  
Axon Membrane ◽  
Trivalent Rare Earth ◽  
Sucrose Gap ◽  
Conductance Changes ◽  
Time Courses ◽  
Conductance Increase

The trivalent rare earth lanthanum was substituted for calcium in the sea water bathing the exterior of an "artificial node" of a lobster axon in a sucrose gap. It caused a progressive rise in threshold, and a decrease in the height of the action potential as well as in its rates of rise and fall. Prolonged application produced an excitation block. Voltage-clamp studies of the ionic currents showed that the time courses of the ionic conductance changes for both sodium and potassium were increased. Concurrently, the potentials at which the conductance increases occurred were shifted to more positive inside values for the La+++ sea water. These effects resemble changes resulting from a high external calcium concentration. Over and above this, La+++ also causes a marked reduction in the maximum amount of conductance increase following a depolarizing potential step. Membrane action potentials similar to those observed experimentally in the La+++ solution have been computed with appropriate parameter changes in the Hodgkin-Huxley equations.

scholarly journals Membrane Potentials of the Lobster Giant Axon Obtained by Use of the Sucrose-Gap Technique

1962 ◽  
Vol 45 (6) ◽  
pp. 1195-1216 ◽  
Author(s):  
Fred J. Julian ◽  
John W. Moore ◽  
David E. Goldman
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Sea Water ◽  
Sucrose Solution ◽  
Chloride Concentration ◽  
Giant Axon ◽  
Membrane Resistance ◽  
Resting Potential ◽  
Gap Technique ◽  
Sucrose Gap

A method similar to the sucrose-gap technique introduced be Stäpfli is described for measuring membrane potential and current in singly lobster giant axons (diameter about 100 micra). The isotonic sucrose solution used to perfuse the gaps raises the external leakage resistance so that the recorded potential is only about 5 per cent less than the actual membrane potential. However, the resting potential of an axon in the sucrose-gap arrangement is increased 20 to 60 mv over that recorded by a conventional micropipette electrode when the entire axon is bathed in sea water. A complete explanation for this effect has not been discovered. The relation between resting potential and external potassium and sodium ion concentrations shows that potassium carries most of the current in a depolarized axon in the sucrose-gap arrangement, but that near the resting potential other ions make significant contributions. Lowering the external chloride concentration decreases the resting potential. Varying the concentration of the sucrose solution has little effect. A study of the impedance changes associated with the action potential shows that the membrane resistance decreases to a minimum at the peak of the spike and returns to near its initial value before repolarization is complete (a normal lobster giant axon action potential does not have an undershoot). Action potentials recorded simultaneously by the sucrose-gap technique and by micropipette electrodes are practically superposable.

scholarly journals Temperature Characteristics of Excitation in Space-Clamped Squid Axons

1966 ◽  
Vol 49 (5) ◽  
pp. 1007-1018 ◽  
Author(s):  
Rita Guttman ◽  
Keyword(s):  
Giant Axon ◽  
Threshold Current ◽  
Threshold Current Density ◽  
Effect Of Temperature ◽  
Axon Membrane ◽  
Temperature Characteristics ◽  
Gap Technique ◽  
Threshold Strength ◽  
Sucrose Gap ◽  
Good Agreement

Temperature characteristics of excitability in the squid giant axon were measured for the space-clamped axon with the double sucrose gap technique. Threshold strength-duration curves were obtained for square wave current pulses from 10 µsec to 10 msec and at temperatures from 5°C to 35°C. The threshold change of potential, at which an action potential separated from a subthreshold response, averaged 17 mv at 20°C with a Q10 of 1.15. The average threshold current density at rheobase was 12 µa/cm2 at 20°C with a Q10 of 2.35 compared to 2.3 obtained previously. At short times the threshold charge was 1.5·10-8 coul/cm2. This was relatively independent of temperature and occasionally showed a minimum in the temperature range. At intermediate times and all temperatures the threshold currents were less than for both the single time constant model and the two factor excitation process as developed by Hill. FitzHugh has made computer investigations of the effect of temperature on the excitation of the squid axon membrane as represented by the Hodgkin-Huxley equations. These are in general in good agreement with our experimental results.

scholarly journals Dynamics of aminopyridine block of potassium channels in squid axon membrane.

1976 ◽  
Vol 68 (5) ◽  
pp. 519-535 ◽  
Author(s):  
J Z Yeh ◽  
G S Oxford ◽  
C H Wu ◽  
T Narahashi
Keyword(s):  
Time Course ◽  
Membrane Surface ◽  
K Channel ◽  
Dependent Manner ◽  
Squid Axon ◽  
Axon Membrane ◽  
K Channels ◽  
Voltage Dependent ◽  
K Current ◽  
Kinetics Of

Aminopyridines (2-AP, 3-AP, and 4-AP) selectively block K channels of squid axon membranes in a manner dependent upon the membrane potential and the duration and frequency of voltage clamp pulses. They are effective when applied to either the internal or the external membrane surface. The steady-state block of K channels by aminopyridines is more complete for low depolarizations, and is gradually relieved at higher depolarizations. The K current in the presence of aminopyridines rises more slowly than in control, the change being more conspicuous in 3-AP and 4-AP than in 2-AP. Repetitive pulsing relieves the block in a manner dependent upon the duration and interval of pulses. The recovery from block during a given test pulse is enhanced by increasing the duration of a conditioning depolarizing prepulse. The time constant for this recovery is in the range of 10-20 ms in 3-AP and 4-AP, and shorter in 2-AP. Twin pulse experiments with variable pulse intervals have revealed that the time course for re-establishment of block is much slower in 3-AP and 4-AP than in 2-AP. These results suggest that 2-AP interacts with the K channel more rapidly than 3-AP and 4-AP. The more rapid interaction of 2-AP with K channels is reflected in the kinetics of K current which is faster than that observed in 3-AP or 4-AP, and in the pattern of frequency-dependent block which is different from that in 3-AP or 4-AP. The experimental observations are not satisfactorily described by alterations of Hodgkin-Huxley n-type gating units. Rather, the data are consistent with a simple binding scheme incorporating no changes in gating kinetics which conceives of aminopyridine molecules binding to closed K channels and being released from open channels in a voltage-dependent manner.

Permeability of the squid axon membrane to several organic molecules

1961 ◽  
Vol 201 (3) ◽  
pp. 413-419 ◽  
Author(s):  
I. Tasaki ◽  
C. S. Spyropoulos
Keyword(s):  
Resting State ◽  
Organic Molecules ◽  
Sea Water ◽  
Repetitive Stimulation ◽  
Potassium Ions ◽  
Univalent Cations ◽  
Squid Axon ◽  
Axon Membrane ◽  
Free Choline ◽  
Order Of Magnitude

The permeability of the squid axon membrane to choline, guanidine, thiourea, urea, sucrose, starch, and cesium was investigated by use of radiotracers. In the resting state, the time constant for the loss of intracellular radioactive (free) choline, guanidine, and cesium was of the same order of magnitude as that for labeled sodium or potassium ions. Choline ion was found to bind rapidly with the constituents of the axon. In sea water containing labeled choline, there was accumulation of radioactivity by the axon. On repetitive stimulation, guanidine and cesium efflux was markedly increased; the choline efflux was slightly increased. Labeled thiourea and urea moved across the membrane far more readily than the univalent cations. Permeation of labeled sucrose and starch was very slow.

Membrane Conductance and Current-Voltage Relation in the Squid Axon Under ‘Voltage-Clamp’

1958 ◽  
Vol 193 (2) ◽  
pp. 318-327 ◽  
Author(s):  
I. Tasaki ◽  
C. S. Spyropoulos
Keyword(s):  
Excited State ◽  
Voltage Clamp ◽  
Time Course ◽  
Membrane Conductance ◽  
Membrane Current ◽  
Sinusoidal Wave ◽  
Squid Axon ◽  
Axon Membrane ◽  
Current Voltage ◽  
Current Voltage Relation

The conductance of the squid axon membrane under ‘voltage-clamp’ was measured by superposing a sinusoidal wave upon rectangular clamping voltage pulses. It was possible to determine the time course of the emf of the membrane under ‘voltage-clamp’ on a single photographic record showing the membrane current together with the simultaneously recorded membrane conductance. The properties of the membrane in the mixed state, in which only a portion of the axon membrane is in the excited state, were investigated by the same method. The property of the weak variable inward membrane current which preceded the appearance of discrete inward surges was investigated.

scholarly journals The exponential tracking and disturbance rejection of the propagated membrane action potential with conductance coefficient feedforward controllers

2021 ◽  
Author(s):  
Weijiu Liu
Keyword(s):  
Action Potential ◽  
Disturbance Rejection ◽  
Surface Membrane ◽  
Potassium Conductance ◽  
Initial Condition ◽  
Membrane Action ◽  
Feedback Controllers ◽  
Pde Model ◽  
Potassium Conductances ◽  
Sodium And Potassium

In the early 1950's, using their experimental data, Hodgkin and Huxley constructed the sodium and potassium conductance feedback controllers for their mathematical model of the flow of electric current through the surface membrane of a giant nerve fibre. In this paper, we re-formulate the construction as a problem of exponential tracking and disturbance rejection and then re-construct new conductance feedforward controllers in the more complicated case of a propagated action potential. The dynamics of the potential is governed by the Hodgkin-Huxley's partial differential equation (PDE) model. The problem is solved for any current disturbances and potential references and conductance coefficient feedforward controllers are designed by using the method of variable transform. It is proved that, under the designed feedforward controllers, the potential tracks exponentially a desired potential reference uniformly on an interval of one unit and the reference satisfies the controlled PDE model except an initial condition. A numerical example shows that the simulated action potential and sodium and potassium conductances are close to the experimental observations.

scholarly journals Selective modification of sodium channel gating in lobster axons by 2, 4, 6-trinitrophenol: Evidence for two inactivation mechanisms.

1975 ◽  
Vol 66 (6) ◽  
pp. 765-779 ◽  
Author(s):  
G S Oxford ◽  
J P Pooler
Keyword(s):  
Time Course ◽  
Sodium Currents ◽  
Voltage Range ◽  
Sodium Conductance ◽  
Gap Technique ◽  
Voltage Curve ◽  
Sucrose Gap ◽  
Sodium Inactivation ◽  
Kinetics Of ◽  
Double Sucrose Gap Technique

Trinitrophernol (TNP) selectively alters the sodium conductance system of lobster giant axons as measured in current clamp and voltage clamp experiments using the double sucrose gap technique. TNP has no measurable effect on potassium currents but reversibly prolongs the time-course of sodium currents during maintained depolarizations over the full voltage range of observable currents. Action potential durations are increased also. Tm of the Hodgkin-Huxley model is not markedly altered during activation of the sodium conductance but is prolonged during removal of activation by repolarization, as observed in sodium tail experiments. The sodium inactivation versus voltage curve is shifted in the hyperpolarizing direction as is the inactivation time constant curve, measured with conditioning voltage steps. This shift speeds the kinetics of inactivation over part of the same voltage range in which sodium currents are prolonged, a contradiction incompatible with the Hodgkin-Huxley model. These results are interpreted as support for a hypothesis of two inactivation processes, one proceeding directly from the resting state and the other coupled to the active state of sodium conductance.

Voltage control during inward current flow in rat ventricular muscle using a double sucrose gap technique

1979 ◽  
Vol 57 (1) ◽  
pp. 124-127 ◽  
Author(s):  
O. F. Schanne ◽  
M. D. Payet ◽  
E. Ruiz P.-Ceretti
Keyword(s):  
Membrane Potential ◽  
Time Course ◽  
Voltage Control ◽  
State Level ◽  
Slow Inward Current ◽  
Ventricular Muscle ◽  
Time Intervals ◽  
Inward Current ◽  
Gap Technique ◽  
Sucrose Gap

In rat ventricular muscle, measurements of the membrane potential with microelectrodes during depolarizing voltage steps showed that deviation of the membrane potential from the command signal were never larger than 15 mV during flow of the fast inward current and that voltage control was regained within 15 ms after the beginning of the voltage step. During the flow of the slow inward current, tail currents elicited by interrupting the time course of the slow current at different time intervals returned exponentially to the steady-state level, thus indicating acceptable voltage control. It is concluded that rat ventricular muscle is a rather favorable preparation for voltage-clamp experiments and this is attributed mainly to the geometry of the preparation.

An Electrophysiological Study of the Sodium and Potassium Permeabilities of Insect Peripheral Nerves

1973 ◽  
Vol 59 (2) ◽  
pp. 447-461
Author(s):  
Y. PICHON ◽  
J. E. TREHERNE
Keyword(s):  
Time Course ◽  
Periplaneta Americana ◽  
Schistocerca Gregaria ◽  
Fat Body ◽  
Electrophysiological Study ◽  
External Potassium ◽  
Sucrose Gap ◽  
Lag Period ◽  
Sodium And Potassium

1. Experiments carried out in situ, using suction electrodes, and in vitro, using the ‘sucrose-gap’, have demonstrated a restricted access of sodium and potassium ions to the axon surfaces in crural nerves of the cockroach Periplaneta americana and the locust Schistocerca gregaria. 2. Elevation of the external potassium concentration produced appreciable extra-neuronal potential changes in intact crural nerves of the locust. 3. In the locust the presence of the over lying fat body sheath was found to alter the time course of potassium-induced d.c. potential changes. 4. In particular, an initial lag period in the d.c. response is described and tentatively interpreted in terms of a cation reservoir effect.

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