scholarly journals EFFECTS OF EXTERNAL IONS ON MEMBRANE POTENTIALS OF A LOBSTER GIANT AXON

1958 ◽  
Vol 41 (3) ◽  
pp. 529-542 ◽  
Author(s):  
John C. Dalton
Keyword(s):  
Action Potential ◽  
Sea Water ◽  
Giant Axon ◽  
Membrane Potentials ◽  
Squid Giant Axon ◽  
Resting Potential ◽  
Magnesium Concentration ◽  
Constant Field ◽  
Order Of Magnitude ◽  
External Calcium

The effects of varying external concentrations of normally occurring cations on membrane potentials in the lobster giant axon have been studied and compared with data presently available from the squid giant axon. A decrease in the external concentration of sodium ions causes a reversible reduction in the amplitude of the action potential and its rate of rise. No effect on the resting potential was detected. The changes are of the same order of magnitude, but greater than would be predicted for an ideal sodium electrode. Increase in external potassium causes a decrease in resting potential, and a decrease in potassium causes an increase in potential. The data so obtained are similar to those which have been reported for the squid giant axon, and cannot be exactly fitted to the Goldman constant field equation. Lowering external calcium below 25 mM causes a reduction in resting and action potentials, and the occasional occurrence of repetitive activity. The decrease in action potential is not solely attributable to a decrease in resting potential. Increase of external calcium from 25 to 50 mM causes no change in transmembrane potentials. Variations of external magnesium concentration between zero and 50 mM had no measurable effect on membrane potentials. These studies on membrane potentials do not indicate a clear choice between the use of sea water and Cole's perfusion solution as the better external medium for studies on lobster nerve.

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 DEMONSTRATION OF TWO STABLE POTENTIAL STATES IN THE SQUID GIANT AXON UNDER TETRAETHYLAMMONIUM CHLORIDE

1957 ◽  
Vol 40 (6) ◽  
pp. 859-885 ◽  
Author(s):  
Ichiji Tasaki ◽  
Susumu Hagiwara
Keyword(s):  
Membrane Potential ◽  
Action Potential ◽  
Membrane Conductance ◽  
Giant Axon ◽  
Membrane Resistance ◽  
Squid Giant Axon ◽  
Resting Potential ◽  
Unstable State ◽  
Stable States ◽  
Tetraethylammonium Chloride

1. Intracellular injection of tetraethylammonium chloride (TEA) into a giant axon of the squid prolongs the duration of the action potential without changing the resting potential (Fig. 3). The prolongation is sometimes 100-fold or more. 2. The action potential of a giant axon treated with TEA has an initial peak followed by a plateau (Fig. 3). The membrane resistance during the plateau is practically normal (Fig. 4). Near the end of the action potential, there is an apparent increase in the membrane resistance (Fig. 5D and Fig. 6, right). 3. The phenomenon of abolition of action potentials was demonstrated in the squid giant axon treated with TEA (Fig. 7). Following an action potential abolished in its early phase, there is no refractoriness (Fig. 8). 4. By the method of voltage clamp, the voltage-current relation was investigated on normal squid axons as well as on axons treated with TEA (Figs. 9 and 10). 5. The presence of stable states of the membrane was demonstrated by clamping the membrane potential with two voltage steps (Fig. 11). Experimental evidence was presented showing that, in an "unstable" state, the membrane conductance is not uniquely determined by the membrane potential. 6. The effect of low sodium water was investigated in the axon treated with TEA (Fig. 12). 7. The similarity between the action potential of a squid axon under TEA and that of the vertebrate cardiac muscle was stressed. The experimental results were interpreted as supporting the view that there are two stable states in the membrane. Initiation and abolition of an action potential were explained as transitions between the two states.

scholarly journals Action of External Divalent Ion Reduction on Sodium Movement in the Squid Giant Axon

1961 ◽  
Vol 45 (1) ◽  
pp. 93-103 ◽  
Author(s):  
William J. Adelman ◽  
John W. Moore
Keyword(s):  
Sea Water ◽  
Giant Axon ◽  
Sodium Concentration ◽  
Squid Giant Axon ◽  
Ion Concentration ◽  
Resting Potential ◽  
Slow Increase ◽  
Sodium Permeability ◽  
Sodium Accumulation ◽  
Sodium Flux

Voltage clamp measurements of the sodium potential have been made on the resting squid giant axon to study the effect of variations in external divalent ion concentration upon net sodium flux. From these measurements the intracellular sodium concentration and the net sodium inflow were calculated using the Nernst relation and constant activity coefficients. While an axon bathed in artificial sea water shows a slow increase in internal sodium concentration, the rate of sodium accumulation is increased about two times by reducing external calcium and magnesium concentrations to 0.1 times their normal values. The mean inward net sodium flux increases from a mean control value of 97 pmole/cm2 sec. to 186 pmole/cm2 sec. in low divalent solution. Associated with these effects of external divalent ion reduction are a marked decrease in action potential amplitude, little or no change in resting potential, and a shift along the voltage axis of the curve relating peak sodium conductance to membrane potential similar to that obtained by Frankenhaeuser and Hodgkin (1957). These results implicate divalent ions in long term (minutes to hours) sodium permeability.

scholarly journals EFFECTS OF EXTERNAL IONS ON MEMBRANE POTENTIALS OF A CRAYFISH GIANT AXON

1959 ◽  
Vol 42 (5) ◽  
pp. 971-982 ◽  
Author(s):  
John C. Dalton ◽  
Keyword(s):  
Action Potential ◽  
Inverse Function ◽  
Giant Axon ◽  
Sodium Concentration ◽  
Resting Potential ◽  
Transmembrane Potentials ◽  
External Potassium ◽  
Ionic Effects ◽  
External Calcium ◽  
Good Agreement

Transmembrane potentials in the crayfish giant axon have been investigated as a function of the concentration of normally occurring external cations. Results have been compared with data already available for the lobster and squid giant axons. The magnitude of the action potential was shown to be a linear function of the log of the external sodium concentration, as would be predicted for an ideal sodium electrode. The resting potential is an inverse function of the external potassium concentration, but behaves as an ideal potassium electrode only at the higher external concentrations of potassium. Decrease in external calcium results in a decrease in both resting potential and action potential; an increase in external calcium above normal has no effect on magnitude of transmembrane potentials. Magnesium can partially substitute for calcium in the maintenance of normal action potential magnitude, but appears to have very little effect on resting potential. All ionic effects studied are completely reversible. The results are in generally good agreement with data presently available for the lobster giant axon and for the squid giant axon.

scholarly journals Some Relations between Action Potential and Resting Potential of the Lobster Giant Axon

1960 ◽  
Vol 43 (3) ◽  
pp. 597-607 ◽  
Author(s):  
J. C. Dalton ◽  
W. J. Adelman
Keyword(s):  
Action Potential ◽  
Initial Conditions ◽  
Giant Axon ◽  
Analog Computer ◽  
Resting Potential ◽  
Quantitative Relation ◽  
High Potassium ◽  
Axon Membrane ◽  
External Potassium ◽  
External Calcium

Experiments were performed to determine the quantitative relation existing between action potential and resting potential of the lobster giant axon. Resting potential changes were induced by either increasing the external potassium concentration or by reducing the external calcium concentration. For either treatment the action potential amplitude is proportional to the logarithm of the resting potential minus a constant. This constant is equivalent to the minimum resting potential at which a propagated spike is possible, and is larger for depolarization in low calcium than in high potassium. Thus the change in action potential per unit change in resting potential is greater in low external calcium than in high external potassium. Analog computer solutions to the Hodgkin-Huxley equations for squid axon membrane potentials show that, if the initial conditions are properly specified, the action potential is proportional to the logarithm of the potassium potential minus a constant. The experimental results and the analog computations suggest that reducing external calcium produces changes in the invertebrate axon that cannot be accounted for solely on the basis of alterations in the potassium potential.

Transmembrane Activity Gradients of K and cl in the Muscle Fibres of Osmoconforming Marine Decapod Crustaceans

1978 ◽  
Vol 72 (1) ◽  
pp. 127-140
Author(s):  
ROBERT W. FREEL
Keyword(s):  
Sea Water ◽  
Membrane Potentials ◽  
Resting Potential ◽  
Muscle Fibres ◽  
Salinity Adaptation ◽  
Decapod Crustaceans ◽  
Marine Crustaceans ◽  
Equilibrium Distributions

1. The resting membrane potentials (Em) and the transmembrane activity gradients for K and Cl were measured in the muscle fibres of osmoconforming (Callianassa and Cancer) and weakly osmoregulating (Pachygrapsus) marine crustaceans acclimated to various osmotic conditions. 2. The muscle membranes of sea water acclimated crabs behave as good K electrodes. However, a slight contribution of Na to the resting potential was demonstrated in all species. The ratio PNa/PK was about 0.01. Equilibrium potentials (measured with ion-selective microelectrodes) for Cl were equal to Em, while EK was always more negative than Em as a result of the slight Na contribution. 3. Acclimation to dilute or concentrated sea water had little effect on the K electrode properties or Na permeabilities of these fibres. The muscle fibres were depolarized in crabs acclimated to concentrated sea water and were hyperpolarized in crabs adapted to dilute sea water. These changes resulted solely from alterations in (aK)i/ (aK)O which were in turn brought about by changes in cellular and haemolymph hydration. 4. Since the Na contribution to Em was so small in all conditions, it was concluded that the distributions of K and Cl are best considered in terms of Donnan equilibria, and that the cellular K and Cl adjustments observed during salinity adaptation reflect the passive re-establishment of new equilibrium distributions for these ions.

Electrophysiology of the Giant Nerve Cell Bodies of Limnaea Stagnalis (L.) (Gastropoda: Pulmonata)

1974 ◽  
Vol 60 (3) ◽  
pp. 653-671
Author(s):  
D. B. SATTELLE
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Cell Types ◽  
Resting Potential ◽  
Constant Field ◽  
Bathing Medium ◽  
Mean Values ◽  
Relative Contribution ◽  
External Potassium ◽  
Limnaea Stagnalis

1. A mean resting potential of -53.3 (S.D. ±2.7) mV has been obtained for 23 neurones of the parietal and visceral ganglia of Limnaea stagnalis (L.). Changes in the resting potential of between 28 and 43 mV accompany tenfold changes in [K+0]. A modified constant-field equation accounts for the behaviour of most cells over the range of external potassium concentrations from 0-5 to 10.o mM/1. Mean values have been estimated for [K+1, 56.2 (S.D.± 9-0) mM/1 and PNa/PK, 0-117 (S.D.±0-028). 2. Investigations on the ionic basis of action potential generation have revealed two cell types which can be distinguished according to the behaviour of their action potentials in sodium-free Ringer. Sodium-sensitive cells are unable to support action potentials for more than 8-10 min in the absence of sodium. Sodium slopes of between 29 and 37 mV per decade change in [Na+0] have been found for these cells. Tetrodotoxin (5 x 10-5 M) usually blocks action potentials in these neurones. Calcium-free inger produces a marked reduction in the overshoot potential and calcium slopes of about 18 mV per decade change in [Ca2+o] are found. Manganous chloride only partially reduces the action potential overshoot in these cells at concentrations of 10 mM/l. 3. Sodium-insensitive neurones maintain action potentials in the absence of external sodium. Stimulation only slightly reduces the amplitude of the action potential under these conditions and such cells are readily accessible to potassium ions in the bathing medium. A calcium-slope of 29 mV per decade change in [Ca2+o] has been observed in these cells in the absence of external sodium. 4. It is concluded that both sodium and calcium ions can be involved in the generation of the action potential in neurones of Limnaea stagnate, their relative contribution varying in different cells.

scholarly journals LONGITUDINAL IMPEDANCE OF THE SQUID GIANT AXON

1941 ◽  
Vol 24 (6) ◽  
pp. 771-788 ◽  
Author(s):  
Kenneth S. Cole ◽  
Richard F. Baker
Keyword(s):  
Sea Water ◽  
Low Frequency ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Dielectric Characteristics ◽  
Impedance Characteristics ◽  
Longitudinal Impedance ◽  
Electrode Length ◽  
Interpolar Distance ◽  
Inductive Reactance

Longitudinal alternating current impedance measurements have been made on the squid giant axon over the frequency range from 30 cycles per second to 200 kc. per second. Large sea water electrodes were used and the inter-electrode length was immersed in oil. The impedance at high frequency was approximately as predicted theoretically on the basis of the poorly conducting dielectric characteristics of the membrane previously determined. For the large majority of the axons, the impedance reached a maximum at a low frequency and the reactance then vanished at a frequency between 150 and 300 cycles per second. Below this frequency, the reactance was inductive, reaching a maximum and then approaching zero as the frequency was decreased. The inductive reactance is a property of the axon and requires that it contain an inductive structure. The variation of the impedance with interpolar distance indicates that the inductance is in the membrane. The impedance characteristics of the membrane as calculated from the measured longitudinal impedance of the axon may be expressed by an equivalent membrane circuit containing inductance, capacity, and resistance. For a square centimeter of membrane the capacity of 1 µf with dielectric loss is shunted by the series combination of a resistance of 400 ohms and an inductance of one-fifth henry.

scholarly journals Relative Ion Permeabilities in the Crayfish Giant Axon Determined from Rapid External Ion Changes

1967 ◽  
Vol 50 (7) ◽  
pp. 1929-1953 ◽  
Author(s):  
Alfred Strickholm ◽  
B. Gunnar Wallin
Keyword(s):  
Membrane Potential ◽  
Potassium Level ◽  
Potassium Concentration ◽  
Giant Axon ◽  
Resting Potential ◽  
Resting Membrane Potential ◽  
Constant Field ◽  
Appreciable Effect ◽  
Ion Concentrations ◽  
External Potassium

The changes in membrane potential of isolated, single crayfish giant axons following rapid shifts in external ion concentrations have been studied. At normal resting potential the immediate change in membrane potential after a variation in external potassium concentration is quite marked compared to the effect of an equivalent chloride change. If the membrane is depolarized by a maintained potassium elevation, the immediate potential change due to a chloride variation becomes comparable to that of an equivalent potassium change. There is no appreciable effect on membrane potential when external sodium is varied, at normal or at a depolarized membrane potential. Starting from the constant field equation, expressions for the permeability ratios PCl/PK, PNa/PK, and for intracellular potassium and chloride concentrations are derived. At normal resting membrane potential, PCl/PK is 0.13 but at a membrane potential of -53 mv (external potassium level increased about five times) it is 0.85. The intracellular concentrations of potassium and chloride are estimated to be 233 and 34 mM, respectively, and it is pointed out that this is not compatible with ions distributed in a Nernst equilibrium across the membrane. It is also stressed that the information given by a plot of membrane potential vs. the logarithm of external potassium concentrations is very limited and rests upon several important assumptions.

scholarly journals Effect of Temperature on the Potential and Current Thresholds of Axon Membrane

1962 ◽  
Vol 46 (2) ◽  
pp. 257-266 ◽  
Author(s):  
Rita Guttman ◽  
Keyword(s):  
Sea Water ◽  
Sucrose Solution ◽  
Giant Axon ◽  
Threshold Current ◽  
Squid Giant Axon ◽  
Effect Of Temperature ◽  
Threshold Potential ◽  
Axon Membrane ◽  
Central Segment ◽  
The Mean

The effect of temperature on the potential and current thresholds of the squid giant axon membrane was measured with gross external electrodes. A central segment of the axon, 0.8 mm long and in sea water, was isolated by flowing low conductance, isoosmotic sucrose solution on each side; both ends were depolarized in isoosmotic KCl. Measured biphasic square wave currents at five cycles per second were applied between one end of the nerve and the membrane of the central segment. The membrane potential was recorded between the central sea water and the other depolarized end. The recorded potentials are developed only across the membrane impedance. Threshold current values ranged from 3.2 µa at 267deg;C to 1 µa at 7.5°C. Threshold potential values ranged from 50 mv at 26°C to 6 mv at 7.5°C. The mean Q10 of threshold current was 2.3 (SD = 0.2), while the Q10 for threshold potentials was 2.0 (SD = 0.1).

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