The interactive effects of fatigue and pH on the ionic conductance of frog sartorius muscle fibers

1985 ◽  
Vol 63 (11) ◽  
pp. 1444-1453 ◽  
Author(s):  
J. M. Renaud ◽  
G. W. Mainwood
Keyword(s):  
Action Potential ◽  
Normal Values ◽  
Muscle Fibers ◽  
Membrane Conductance ◽  
Interactive Effects ◽  
Resting Potential ◽  
Sartorius Muscle ◽  
Ionic Conductance ◽  
Frog Sartorius Muscle ◽  
Frog Sartorius

The effects of fatigue on the membrane conductance of frog sartorius muscle at the resting potential and during an action potential were studied. When muscles were exposed to an extracellular pH of 8.0 the membrane conductance at the resting potential increased during fatigue by about 20% and returned to prefatigue level in about 20 min. The membrane conductance of muscle fibers exposed to pH 6.4 was about three times less than that of pH 8.0 and decreased further during fatigue. Furthermore, the recovery of a normal membrane conductance was slow at pH 6.4. Both the inward, depolarizing and the outward, repolarizing currents during the action potential are reduced in fatigue. In each case the effect is greater at pH 6.4 than at 8.0 and recovery towards normal values is slower at pH 6.4. It is concluded that the ionic conductance of the sareolemmal membrane at the resting potential and during an action potential are modified by fatigue and that these changes are modulated by pHo.

Effect of dinitrophenol on phosphorylation and bioelectric phenomena of excitable tissues

1961 ◽  
Vol 200 (3) ◽  
pp. 431-436 ◽  
Author(s):  
L. G. Abood ◽  
K. Koketsu ◽  
K. Noda
Keyword(s):  
Energy Metabolism ◽  
Muscle Fibers ◽  
Resting Potential ◽  
Sartorius Muscle ◽  
Nerve Roots ◽  
Intracellular Potassium ◽  
Frog Sartorius Muscle ◽  
Anodal Polarization ◽  
Frog Sartorius

The effect of 2, 4-dinitrophenol (DNP) was investigated on the phosphorylation of frog sartorius muscle and ventral nerve roots, using P32 as a tracer. It was possible almost completely to inhibit phosphorylation without significantly altering excitability, although the resting potential and intracellular potassium decreased over 30%. The addition of 0.01 mm DNP to a sodium-free hydrazinium system completely blocked excitability, despite the fact that this concentration of DNP produced no further inhibition of phosphorylation. It was possible to restore the excitability of frog sartorius muscle fibers by anodal polarization after the fibers were rendered inexcitable by immersion in 1 mm DNP. The results were discussed in terms of the role of energy metabolism in excitability and other bioelectric phenomena of muscle and nerve.

Action of acetylcholine, choline and D-tubocurarine on the membrane of frog sartorius muscle fibers

1959 ◽  
Vol 196 (6) ◽  
pp. 1191-1196 ◽  
Author(s):  
S. Ochs ◽  
A. K. Mukherjee
Keyword(s):  
Membrane Potential ◽  
Mechanical Stimulation ◽  
Muscle Fibers ◽  
Potential Drop ◽  
Sartorius Muscle ◽  
End Plate ◽  
Frog Sartorius Muscle ◽  
Before And After ◽  
The Mean ◽  
Frog Sartorius

Resting potentials of frog sartorius muscle fibers were taken with microelectrodes at different distances along the length of muscles before and after adding acetylcholine or choline. The mean membrane potential drop and scatter of the potentials recorded in the relatively nerve-free, and in the more densely innervated parts of the muscle, were similar. The loss of direct excitability to electrical and mechanical stimulation was correlated with the concentration of choline or acetylcholine presented. d-tubocurarine added beforehand protected against the depolarizing effect of acetylcholine and choline everywhere along the length of the muscle. A generalized action of acetylcholine and choline and also of d-tubocurarine all along the muscle fibers was inferred. This generalized action at higher concentrations of acetylcholine and choline is believed to be additional to a more specific end plate action.

Effects of antipsychotic drugs on action potential production in skeletal muscle. I. Chlorpromazine and promethazine

1977 ◽  
Vol 55 (3) ◽  
pp. 452-461 ◽  
Author(s):  
H. S. Buttar ◽  
G. B. Frank
Keyword(s):  
Action Potential ◽  
Muscle Fibers ◽  
Potassium Conductance ◽  
Input Resistance ◽  
Threshold Current ◽  
Resting Potential ◽  
Sartorius Muscle ◽  
Potential Production ◽  
Drug Concentrations ◽  
Local Anaesthetic Effect

The effects of chlorpromazine, an antipsychotic phenothiazine, and promethazine, an antihistaminic phenothiazine, on excitability and action potential production in frog's sartorius muscle fibers were studied and compared. Both drugs produced a local anaesthetic effect which developed slowly over 3 to 5 h with lower concentrations (1 to 15 × 10−6 M) and was only partially reversed by exposing the muscles to a drug-free solution for 3 to 4 h. The resting potential and the input resistance of the muscle fibers were unaffected by drug concentrations which reduced the action potential maximum rate of rise, the threshold current of 2-ms injected pulses and the intracellularly measured threshold depolarization. The effects on the action potential were antagonized in an apparently competitive manner by sodium ions. Thus both drugs depressed excitability and the rising phase of the action potential by inhibiting the specific increase in sodium conductance (gNa) which normally follows an adequate stimulus. It was shown that both drugs also inhibited the secondary rise in potassium conductance (gK) which normally occurs during an action potential. Although quantitatively similar, lower concentrations of chlorpromazine (> 15 × 10−6 M) were more potent and higher concentrations (> 15 × 10−6 M) were less potent than promethazine. The qualitatively identical and the quantitatively similar effects of these two drugs would suggest that the antipsychotic effect produced by some of the phenothiazines is unrelated to their effects on action potential production.

Effects of K+ on the twitch and tetanic contraction in the sartorius muscle of the frog, Rana pipiens. Implication for fatigue in vivo

1992 ◽  
Vol 70 (9) ◽  
pp. 1236-1246 ◽  
Author(s):  
Jean Marc Renaud ◽  
Peter Light
Keyword(s):  
Action Potential ◽  
Action Potentials ◽  
Muscle Fibers ◽  
Resting Potential ◽  
Sartorius Muscle ◽  
Coupling Mechanism ◽  
Tetanic Force ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
The Mean

The effects of increasing the extracellular K+ concentration on the capacity to generate action potentials and to contract were tested on unfatigued muscle fibers isolated from frog sartorius muscle. The goal of this study was to investigate further the role of K+ in muscle fatigue by testing whether an increased extracellular K+ concentration in unfatigued muscle fibers causes a decrease in force similar to the decrease observed during fatigue. Resting and action potentials were measured with conventional microelectrodes. Twitch and tetanic force was elicited by field stimulation. At pHo (extracellular pH) 7.8 and 3 mmol K+∙L−1 (control), the mean resting potential was −86.6 ± 1.7 mV (mean ± SEM) and the mean overshoot of the action potential was 5.6 ± 2.5 mV. An increased K+ concentration from 3 to 8.0 mmol∙L−1 depolarized the sarcolemma to −72.2 ± 1.4 mV, abolished the overshoot as the peak potential during an action potential was −12.0 ± 3.9 mV, potentiated the twitch force by 48.0 ± 5.7%, but did not affect the tetanic force (maximum force) and the ability to maintain a constant force during the plateau phase of a tetanus. An increase to 10 mmol K+∙L−1 depolarized the sarcolemma to −70.1 ± 1.7 mV and caused large decreases in twitch (31.6 ± 26.1%) and tetanic (74.6 ± 12.1%) force. Between 3 and 9 mmol K+∙L−1, the effects of K+ at pHo 7.2 (a pHo mimicking the change in interstitial pH during fatigue) and 6.4 (a pHo known to inhibit force recovery following fatigue) on resting and action potentials as well as on the twitch and tetanic force were similar to those at pHo 7.8. Above 9 mmol K+∙L−1 significant differences were found in the effect of K+ between pHo 7.8 and 7.2 or 6.4. In general, the decrease in peak action potential and twitch and tetanic force occurred at higher K+ concentrations as the pHo was more acidic. The results obtained in this study do not support the hypothesis that an accumulation of K+ at the surface of the sarcolemma is sufficiently large to suppress force development during fatigue. The possibility that the K+ concentration in the T tubules reaches the critical K+ concentration necessary to cause a failure of the excitation–contraction coupling mechanism is discussed.Key words: excitation–contraction coupling, fatigue, potassium, tetanus, twitch.

Electrophysiological, morphometric, and histochemical characteristics of muscle fibers of the frog sartorius muscle

1978 ◽  
Vol 86 (4) ◽  
pp. 1270-1274 ◽  
Author(s):  
A. L. Zefirov ◽  
N. P. Rezvyakov ◽  
G. I. Poletaev ◽  
E. G. Ulumbekov ◽  
E. M. Volkov
Keyword(s):  
Muscle Fibers ◽  
Sartorius Muscle ◽  
Frog Sartorius Muscle ◽  
Frog Sartorius
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