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February 1972

Corticosteroids: Effects on Muscle Membrane Excitability

Author Affiliations

Tucson, Ariz
From the Department of Physiology, Division of Neurology, University of Arizona College of Medicine, Tucson, Ariz.

Arch Neurol. 1972;26(2):181-185. doi:10.1001/archneur.1972.00490080099012

Membrane resting and action potentials were recorded intracellularly from extensor digitorum longus (EDL) and soleus (SOL) muscles of mice subjected to dexamethasone administration. The mean resting potential was diminished in EDL fibers from treated animals, while SOL fibers were not affected. Action potential measurements at controlled membrane polarization showed alteration in excitability of treated EDL fibers since excitation threshold was greater than in control fibers and the potential at which action potentials could no longer be evoked was higher. These findings could result from changes in resting membrane permeability or internal ion concentration in type II fibers of corticosteroid-treated animals. In addition, the regenerative conductance mechanism is affected such that the potential-dependent excitability is shifted to a more hyperpolarized region. These simultaneous changes result in diminution of membrane excitability, contributing to muscle dysfunction.

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