What question did this study set out to answer?

To determine how varying extracellular sodium and calcium concentrations influence the reversal potential and single channel conductance of acetylcholine-activated channels at the neuromuscular junction.

January 1, 1979The Journal of PhysiologyOpen Access

Ion‐concentration dependence of the reversal potential and the single channel conductance of ion channels at the frog neuromuscular junction.

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Authors

CLC. A. LewisRiverview Medical Center

Discussion

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Overview

Electrophysiological study demonstrates ion-dependent conductance and reversal potentials in frog neuromuscular junctions, indicating ion interactions within acetylcholine channels.

Key Points

To determine how varying extracellular sodium and calcium concentrations influence the reversal potential and single channel conductance of acetylcholine-activated channels at the neuromuscular junction.
Performed voltage-clamp recordings on isolated single muscle fibres from Rana pipiens cutaneous pectoris preparations.
Calculated single channel conductance using noise analysis across varied membrane potentials and external ionic conditions.
Evaluated empirical measurements against theoretical permeation frameworks, including constant field theory, a modified Takeuchi model, and single barrier theory.
Reversal potential in normal sodium Ringer was -3.8 ± 0.5 mV (n = 22) and declined approximately linearly with the logarithm of external sodium activity down to 10% of normal.
Single channel conductance was 27.5 ± 0.7 pS (n = 28) in normal Ringer and plateaued near 10 pS when sodium was replaced with sucrose.
Elevating external calcium from 2 to 10 mM shifted the reversal potential to more positive values and reduced single channel conductance, disproving standard independent-flux permeation models.

Cite This Study

C. A. Lewis (1979) studied this question.

synapsesocial.com/papers/6a6f173635aa2c282ce07ef6 https://doi.org/10.1113/jphysiol.1979.sp012629

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January 1, 1979The Journal of PhysiologyOpen Access

Ion‐concentration dependence of the reversal potential and the single channel conductance of ion channels at the frog neuromuscular junction.

View Full Paper

Ask AI

Bookmark

Authors

CLC. A. LewisRiverview Medical Center

Discussion

Member takes

Overview

Electrophysiological study demonstrates ion-dependent conductance and reversal potentials in frog neuromuscular junctions, indicating ion interactions within acetylcholine channels.

Key Points

To determine how varying extracellular sodium and calcium concentrations influence the reversal potential and single channel conductance of acetylcholine-activated channels at the neuromuscular junction.
Performed voltage-clamp recordings on isolated single muscle fibres from Rana pipiens cutaneous pectoris preparations.
Calculated single channel conductance using noise analysis across varied membrane potentials and external ionic conditions.
Evaluated empirical measurements against theoretical permeation frameworks, including constant field theory, a modified Takeuchi model, and single barrier theory.
Reversal potential in normal sodium Ringer was -3.8 ± 0.5 mV (n = 22) and declined approximately linearly with the logarithm of external sodium activity down to 10% of normal.
Single channel conductance was 27.5 ± 0.7 pS (n = 28) in normal Ringer and plateaued near 10 pS when sodium was replaced with sucrose.
Elevating external calcium from 2 to 10 mM shifted the reversal potential to more positive values and reduced single channel conductance, disproving standard independent-flux permeation models.

Cite This Study

C. A. Lewis (1979) studied this question.

synapsesocial.com/papers/6a6f173635aa2c282ce07ef6 https://doi.org/10.1113/jphysiol.1979.sp012629

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