scholarly journals The Ionic Mechanisms of Hyperpolarizing Responses in Lobster Muscle Fibers

1961 ◽  
Vol 45 (2) ◽  
pp. 243-265 ◽  
Author(s):  
J. P. Reuben ◽  
R. Werman ◽  
H. Grundfest
Keyword(s):  
Membrane Permeability ◽  
Muscle Fibers ◽  
Membrane Resistance ◽  
Oscillatory Behavior ◽  
Current Leads ◽  
Oscillatory Characteristic ◽  
Ionic Mechanisms ◽  
External K

Lobster muscle fibers develop hyperpolarizing responses when subjected to sufficiently strong hyperpolarizing currents. In contrast to axons of frog, toad, and squid, the muscle fibers produce their responses without the need for prior depolarization in high external K+. Responses begin at a threshold polarization (50 to 70 mv), the potential reaching 150 to 200 mv hyperpolarization while the current remains constant. The increased polarization develops at first slowly, then becomes rapid. It usually subsides from its peak spontaneously, falling temporarily to a potential less hyperpolarized than at threshold for the response. As long as current is applied there can be oscillatory behavior with sequential rise and subsidence of the polarization, repeating a number of times. Withdrawal of current leads to rapid return of the potential to the resting level and a small, brief depolarization. Associated with the latter, but of longer duration, is an increased conductance whose magnitude and duration increase with the antecedent current. Hyperpolarizing responses of lobster muscle fibers are due to increased membrane resistance caused by hyperpolarizing K inactivation. The oscillatory characteristic of the response is due to a delayed superimposed and prolonged increase in membrane permeability, probably for Na+ and for either K+ or Cl-. The hyperpolarizing responses of other tissues also appear to result from hyperpolarizing K inactivation, on which is superimposed an increased conductance for some other ion or ions.

Electric current generated by squid giant axon sodium pump: external K and internal ADP effects

1978 ◽  
Vol 235 (1) ◽  
pp. C63-C68 ◽  
Author(s):  
R. F. Abercrombie ◽  
P. de Weer
Keyword(s):  
Sodium Pump ◽  
Giant Axon ◽  
Pump Current ◽  
Membrane Resistance ◽  
Extracellular Potassium ◽  
Sodium Efflux ◽  
Steroid Sensitive ◽  
External Potassium ◽  
Loligo Pealei ◽  
External K

The operation of the sodium pump of giant axons of the squid, Loligo pealei, has been studied simultaneously in two independent ways: 1) by measuring sodium efflux with 22Na, and 2) by calculating the transmembrane current generated by the pump from measurements of membrane resistance and digitalis-sensitive membrane potential. In normal, untreated axons, the effect of increasing the external potassium concentration on both sodium efflux and pump current is similar, which suggests that Na:K pump stoichiometry remains relatively constant in the range of 0-20 mM external K. The data are compatible with a 3:2 Na:K ratio. In axons whose intracellular ADP level has been elevated by injection of L-arginine, a large, electrically silent, cardiotonic steroid-sensitive sodium efflux takes place in the absence of external potassium; this suggests that pump-mediated Na:Na exchange is 1:1 or electroneutral. Finally, elevation of external potassium levels causes the appearance, in high-ADP axons, of electrogenic pumping, with little effect on sodium efflux; hence, in contrast to what is seen in normal (low-ADP) axons, the charge translocated, per sodium ion extruded, increases sharply with increasing extracellular potassium levels.

scholarly journals Effect of acetylcholine on postjunctional membrane permeability in eel electroplaque.

1977 ◽  
Vol 70 (1) ◽  
pp. 23-36 ◽  
Author(s):  
N L Lassignal ◽  
A R Martin
Keyword(s):  
Field Equation ◽  
Membrane Potential ◽  
Membrane Permeability ◽  
Ionic Composition ◽  
Reversal Potential ◽  
Resting Potential ◽  
Constant Field ◽  
Free Solution ◽  
Positive Direction ◽  
External K

Acetylcholine (ACh) was applied iontophoretically to the innervated face of isolated eel electroplaques while the membrane potential was being recorded intracellularly. At the resting potential (about -85 mV) application of the drug produced depolarizations (ACh potentials) of 20 mV or more which became smaller when the membrane was depolarized and reversed in polarity at about zero membrane potential. The reversal potential shifted in the negative direction when external Na+ was partially replaced by glucosamine. Increasing external K+ caused a shift of reversal potential in the positive direction. It was concluded that ACh increased the permeability of the postjunctional membrane to both ions. Replacement of Cl- by propionate had no effect on the reversal potential. In Na+-free solution containing glucosamine the reversal potential was positive to the resting potential, suggesting that ACh increased the permeability to glucosamine. Addition of Ca++ resulted in a still more positive reversal potential, indicating an increased permeability to Ca++ as well. Analysis of the results indicated that the increases in permeability of the postjunctional membrane to K+, Na+, Ca++, and glucosamine were in the ratios of approximately 1.0:0.9:0.7:0.2, respectively. With these permeability ratios, all of the observed shifts in reversal potential with changes in external ionic composition were predicted accurately by the constant field equation.

scholarly journals Capacitance of the Surface and Transverse Tubular Membrane of Frog Sartorius Muscle Fibers

1969 ◽  
Vol 53 (3) ◽  
pp. 265-278 ◽  
Author(s):  
Peter W. Gage ◽  
Robert S. Eisenberg
Keyword(s):  
Electrical Properties ◽  
Time Course ◽  
Muscle Fibers ◽  
Membrane Resistance ◽  
Ringer Solution ◽  
Sartorius Muscle ◽  
Tubular Membrane ◽  
Essentially Normal ◽  
The Difference ◽  
Passive Electrical Properties

The passive electrical properties of glycerol-treated muscle fibers, which have virtually no transverse tubules, were determined. Current was passed through one intracellular microelectrode and the time course and spatial distribution of the resulting potential displacement measured with another. The results were analyzed by using conventional cable equations. The membrane resistance of fibers without tubules was 3759 ± 331 ohm-cm2 and the internal resistivity 192 ohm-cm. Both these figures are essentially the same as those found in normal muscle fibers. The capacitance of the fibers without tubules is strikingly smaller than normal, being 2.24 ± 0.14 µF/cm2. Measurements were also made of the passive electrical properties of fibers in a Ringer solution containing 400 mM glycerol (which is used in the preparation of glycerol-treated fibers). The membrane resistance and capacitance are essentially normal, but the internal resistivity is somewhat reduced. These results show that glycerol in this concentration does not directly affect the membrane capacitance. Thus, the figure for the capacitance of glycerol-treated fibers, which agrees well with previous estimates made by different techniques, represents the capacitance of the outer membrane of the fiber. Estimates of the capacitance per unit area of the tubular membrane are made and the significance of the difference between the figures for the capacitance of the surface and tubular membrane is discussed.

Electrical properties of diaphragm and EDL muscles during the life of dystrophic mice

1997 ◽  
Vol 272 (1) ◽  
pp. C333-C340 ◽  
Author(s):  
A. De Luca ◽  
S. Pierno ◽  
D. C. Camerino
Keyword(s):  
Electrical Properties ◽  
Muscle Fibers ◽  
Potassium Conductance ◽  
Membrane Resistance ◽  
Membrane Excitability ◽  
Hindlimb Muscles ◽  
Age Related ◽  
Edl Muscle ◽  
And Control ◽  
Dystrophic Mice

The membrane electrical properties of diaphragm and extensor digitorum longus (EDL) muscle fibers of dystrophic mdx and control mice from 4 wk to 14-19 mo of age were recorded with the intracellular microelectrode technique. Up to 8 wk of age, the diaphragm and EDL muscles did not differ between the two strains. From 8 up to 20 wk, the mdx diaphragm fibers showed a higher membrane resistance (Rm), which was due to significantly lower values of resting chloride conductance (GCl) and an overexcitability with respect to age-matched controls. Oppositely, the mdx EDL muscle fibers had significantly lower Rm and higher GCl values than age-related controls at 8, 10, and 13 wk, along with a decreased membrane excitability. These differences were no longer detectable at 20 wk. The diaphragm and EDL muscles from 14- to 19-mo-old controls showed a decrease of GCl and an increase of potassium conductance with respect to adult animals. In aged mdx animals, these changes were very dramatic in diaphragm fibers, whereas no differences, with respect to adults, were found in the EDL muscle. Thus GCl is an index of the dystrophic condition of mdx muscles. In the degenerating diaphragm, the impairment of GCl can account for some of the pathological features of the muscle. In the EDL muscle, the changes of GCl can follow the high regenerative potential of the hindlimb muscles of the mdx phenotype.

Stabilization and rectification of muscle fiber membrane by tetrodotoxin

1960 ◽  
Vol 198 (5) ◽  
pp. 934-938 ◽  
Author(s):  
Toshio Narahashi ◽  
Takehiko Deguchi ◽  
Norimoto Urakawa ◽  
Yoshio Ohkubo
Keyword(s):  
Muscle Fiber ◽  
Muscle Fibers ◽  
Membrane Resistance ◽  
Frog Muscle ◽  
Resting Potential ◽  
Fiber Membrane ◽  
Delayed Rectification ◽  
Intracellular Microelectrodes ◽  
Cathodal Current ◽  
Muscle Fiber Membrane

The mode of action of tetrodotoxin on the frog muscle fiber membrane has been analyzed with the aid of intracellular microelectrodes. Tetrodotoxin of 10–7 concentration made the applied cathodal current ineffective in producing action potential, whereas the resting potential and resting membrane resistance underwent little or no change. With 10–8 tetrodotoxin the muscle fibers responded with the small action potentials at high critical depolarizations. These results can be explained on the basis of the membrane being stabilized by inactivation of the sodium-carrying mechanism. Although delayed rectification was not observed in normal muscle fibers, it became apparent in the fibers rendered inexcitable by tetrodotoxin. This finding, together with other evidence in the existing literature, supports an applicability of the sodium theory to the frog muscle fibers.

Ionic basis of different synaptic potentials mediated by an identified dopamine-containing neuron in Planorbis

1979 ◽  
Vol 203 (1153) ◽  
pp. 427-444 ◽  
Keyword(s):  
Sharp Increase ◽  
Membrane Conductance ◽  
Membrane Resistance ◽  
Inhibitory Response ◽  
Dopamine Neuron ◽  
Electrical Transmission ◽  
Planorbis Corneus ◽  
K Concentration ◽  
Ionic Basis ◽  
External K

A specified dopamine neuron in Planorbis corneus produces dopaminemediated e.p.s.ps, i.p.s.ps or biphasic, depolarizing-hyperpolarizing p.s.ps in different follower neurons. The excitatory potentials were of three types. Some follower neurons exhibited slow e.p.s.ps (ca. 1 s), and a long-lasting, slowly desensitizing, depolarizing response to iontophoresed dopamine. Others showed rapid (ca. 150 ms) e.p.s.ps, often of variable amplitude, and a rapid, quickly desensitizing, response to iontophoresed dopamine. The rapid e.p.s.ps were sometimes followed by the inhibitory response (biphasic potential). The e.p.s.ps were potentiated by hyperpolarization and reduced by depolarization, though they could not be inverted. The slow e.p.s.p. was shown to be associated with an increase in membrane conductance, but it has proved difficult to elucidate the ions involved. A third type of e.p.s.p. was produced by electrical transmission. The inhibitory potentials were generally reduced in amplitude by artificial hyperpolarization but could rarely be inverted. This is probably due in part to the presence of electrotonic coupling between these follower neurons. The i.p.s.ps were associated with an increase in conductance which appeared small when measured in the cell body. However, the i.p.s.ps produced considerable shunting of electrotonic transmission between coupled followers indicating a large increase in conductance at the synapse. I.p.s.ps were unaffected by Cl-free solution but they were greatly reduced, though rarely inverted, by increasing the external K concentration. They were blocked by intracellular tetraethylammonium, or cooling. The effects on corresponding responses to iontophoresed dopamine were in each case the same as on the i.p.s.ps. It is concluded that the i.p.s.ps mediated by the dopamine neuron are produced by an increase in permeability to K+. On a few occasions i.p.s.ps mediated by the dopamine neuron were potentiated by hyperpolarization. This appeared to be caused by a sharp increase in membrane resistance with hyperpolarization of these particular neurons. However, mediation by a mechanism of conductance decrease could not be completely excluded.

scholarly journals Graded and All-or-None Electrogenesis in Arthropod Muscle

1961 ◽  
Vol 44 (5) ◽  
pp. 997-1027 ◽  
Author(s):  
R. Werman ◽  
H. Grundfest
Keyword(s):  
Muscle Fibers ◽  
Relative Increase ◽  
Ion Flux ◽  
Alkali Earth ◽  
Low Concentrations ◽  
Na Inactivation ◽  
High Conductance ◽  
External K

Conversion of graded responsiveness of lobster muscle fibers to all-or-none activity by alkali-earth and tetraethylammonium (TEA) ions appears to be due to a combination of effects. The membrane is hyperpolarized, its resistance is increased, and its sensitivity to external K+ is diminished, all effects which indicate diminished K+ conductance. While the spikes are prolonged, the conductance is higher throughout the response than it is in the resting membrane. Repetitive activity becomes prominent. These effects indicate maintained high conductance for an ion which causes depolarization. This is normally Na+, since its presence in low concentrations potentiates the effects of Ba++, but the alkali-earth ions and TEA can also carry inward charge. Ba++, Sr++, and TEA appear to be more effective than is Ca++ in its normal role, which is probably to depress K+ conductance and Na inactivation. Thus, conversion of graded to all-or-none responsiveness appears to occur because of the relative increase of depolarizing inward ion flux and decrease of repolarizing outward flux.

scholarly journals Resolution of the potassium ion pump in muscle fibers using barium ions.

1975 ◽  
Vol 66 (3) ◽  
pp. 269-286 ◽  
Author(s):  
R A Sjodin ◽  
O Ortiz
Keyword(s):  
Membrane Permeability ◽  
Passive Movement ◽  
Ion Pump ◽  
Pumping Rate ◽  
Barium Ions ◽  
Rectangular Hyperbola ◽  
Wide Range ◽  
Na Ions ◽  
Frog Sartorius ◽  
External K

When frog sartorius muscles recover from Na enrichment in the presence of external K, net K entry into the fibers occurs by both passive movement and active inward transport via a K pump. Under normal conditions, it has not been possible to experimentally distinguish these processes. Fractionation into the flux components must be accomplished from inferences concerning the K conductance or permeability during a period of rapid Na extrusion. The best estimates indicate that 60-80% of the K entry occurs via the K pump. In the presence of Ba ions, the membrane permeability to K is very much reduced. Under these conditions, Na-enriched muscles underwent a normal recovery in the presence of external K, and the amount of inward K movement due to the K pump rose to over 90% of the total K entry. The characteristics of the K pump studied by this means were: (a) essentially complete inhibition by 10(-4) M ouabain, (b) inhibition by [Na]omicron, (c) activation by [K]omicron according to a rectangular hyperbola in the absence of [Na]omicron, (d) linear activation by [Na]iota over a wide range in concentration, (e) zero or undetectably low pumping rate as [Na]iota leads to 0, (f) the number of Na ions actively transported per K ion actively transported is 1.4-1.7 normally and 1.1 in the presence of Ba.

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