In vivo assessment of muscle membrane properties in the sodium channel myotonias.
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BORIS DOI
Publisher DOI
PubMed ID
28877545
Description
INTRODUCTION
The gain-of-function mutations that underlie sodium channel myotonia (SCM) and paramyotonia congenital (PMC) produce differing clinical phenotypes. We used muscle velocity recovery cycles (MVRCs) to investigate membrane properties.
METHODS
MVRCs and responses to trains of stimuli were compared in patients with SCM (n = 9), PMC (n = 8), and normal controls (n = 26).
RESULTS
The muscle relative refractory period was reduced in SCM, consistent with faster recovery of the mutant sodium channels from inactivation. Both SCM and PMC showed an increased early supernormality and increased mean supernormality following multiple conditioning stimuli, consistent with slowed sodium channel inactivation. Trains of fast impulses caused a loss of amplitude in PMC, after which only half of the muscle fibers recovered, suggesting that the remainder stayed depolarized by persistent sodium currents.
DISCUSSION
The differing effects of mutations on sodium channel function can be demonstrated in human subjects in vivo using this technique. Muscle Nerve, 2017.
The gain-of-function mutations that underlie sodium channel myotonia (SCM) and paramyotonia congenital (PMC) produce differing clinical phenotypes. We used muscle velocity recovery cycles (MVRCs) to investigate membrane properties.
METHODS
MVRCs and responses to trains of stimuli were compared in patients with SCM (n = 9), PMC (n = 8), and normal controls (n = 26).
RESULTS
The muscle relative refractory period was reduced in SCM, consistent with faster recovery of the mutant sodium channels from inactivation. Both SCM and PMC showed an increased early supernormality and increased mean supernormality following multiple conditioning stimuli, consistent with slowed sodium channel inactivation. Trains of fast impulses caused a loss of amplitude in PMC, after which only half of the muscle fibers recovered, suggesting that the remainder stayed depolarized by persistent sodium currents.
DISCUSSION
The differing effects of mutations on sodium channel function can be demonstrated in human subjects in vivo using this technique. Muscle Nerve, 2017.
Date of Publication
2018-04
Publication Type
Article
Subject(s)
Keyword(s)
channelopathy membrane potential myotonia paramyotonia congenita sodium channel velocity recovery cycle
Language(s)
en
Contributor(s)
Tan, S Veronica | |
Hanna, Michael G | |
Bostock, Hugh |
Additional Credits
Series
Muscle & nerve
Publisher
John Wiley & Sons
ISSN
0148-639X
Access(Rights)
restricted