Role of Cholesterol in the Maintenance of Endplate Electrogenesis in Rat Diaphragm

Methyl-beta-cyclodextrin (0.1 mM) reduced resting potential of muscle fibers and abolished local endplate membrane hyperpolarization in rat diaphragm. This effect was associated with selective reduction of electrogenic activity of alpha 2-isoform of Na,K-ATPase without changes in the level of intracellular acetylcholine. Experiments with cholesterol marker filipin showed that methyl-beta-cyclodextrin in this dose induced cholesterol translocation from lipid rafts to liquid phase of the membrane without its release into extracellular space. This modification of lipid rafts by methyl-beta-cyclodextrin presumably impaired the mechanism maintaining electrogenesis in endplates mediated by modulation of Na,K-ATPase by non-quantum acetylcholine. Cholesterol can serve as a molecular component of this mechanism.