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Electrophysiologic properties of intercostal muscle fibers in human neuromuscular diseases
Author(s) -
Gruener Raphael,
Stern Lawrence Z.,
Markovitz David,
Gerdes Clarence
Publication year - 1979
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880020303
Subject(s) - myotonia congenita , spike potential , myotonia , depolarization , tetrodotoxin , intercostal muscle , myotonic dystrophy , membrane potential , motor neuron , compound muscle action potential , electrophysiology , neuromuscular transmission , medicine , sural nerve , duchenne muscular dystrophy , resting potential , anatomy , chemistry , neuroscience , biology , disease , respiratory system
Electrophysiologic properties of biopsied normal and diseased intercostal muscle fibers were examined using intracellular microelectrode techniques. The resting potentials of all diseased muscle fibers were found to be depolarized. Those from Duchenne dystrophy patients showed the largest depolarization, followed by those from patients with myotonic muscular dystrophy, myotonia congenita, and motor neuron disease. All of the diseased fibers except those from myotonia congenita patients demonstrated an impaired ability to generate action potentials. In the latter fibers, the higher‐than‐normal membrane resistance was associated with hyperexcitability. When the membrane was hyperpolarized to the normal range, however, action potential characteristics in all fibers were near normal, except in motor neuron disease. All action potentials were blocked by tetrodotoxin. These findings—i.e., that all fibers were capable of generating action potentials when hyperpolarized, and that all action potentials were blocked by tetrodotoxin—suggest the relative intactness, in the disease studied here, of the regenerative sodium conductance mechanism.