Jun 1, 1975

Ionic properties of the acetylcholine receptor in cultured rat myotubes

The Journal of General Physiology
A K Ritchie, D M Fambrough

Abstract

The acetylcholine reversal potential (Er) of cultured rat myotubes is -3mV. When activated, the receptor is permeable to K+ and Na+, but not to Cl- ions. Measurement of Er in Tris+-substituted, Na-free medium also indicated a permeability to Tris+ ions. Unlike adult frog muscle the magnitude of Er was insensitive to change in external Ca++ (up to 30 mM) or to changes in external pH (between 6.4 and 8.9). The equivalent circuit equation describing the electrical circuit composed of two parallel ionic batteries (EK and ENa) and their respective conductances (gK and gNa), which has been generally useful in describing the Er of adult rat and frog muscle, could also be applied to rat myotubes when Er was measured over a wide range of external Na+ concentrations. The equivalent circuit equation could not be applied to myotubes bathed in media of different external K+ concentrations. In this case, the Er was more closely described by the Goldman constant field equation. Under certain circumstances, it is known that the receptor in adult rat and frog muscle can be induced to reversibly shift from behavior described by the equivalent circuit equation to that described by the Goldman equation. Attempts to similarly manipulate the respons...Continue Reading

Mentioned in this Paper

Chloride Ion Level
Calcium
Resting Potentials
Potassium
Cholinergic Receptors
Culture Techniques
Sodium
Muscle
Electrophysiology (Science)
kappa-Bungarotoxin

About this Paper

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