Chloride channels in myotonia congenita assessed by velocity recovery cycles
Authors:
Open Access
- 4 September 2013
- journal article
- research article
- Published by Wiley in Muscle & Nerve
- Vol. 49 (6) , 845-857
Abstract
Introduction: Myotonia congenita (MC) is caused by congenital defects in the muscle chloride channel CLC‐1. This study used muscle velocity recovery cycles (MVRCs) to investigate how membrane function is affected. Methods: MVRCs and responses to repetitive stimulation were compared between 18 patients with genetically confirmed MC (13 recessive, 7 dominant) and 30 age‐matched, normal controls. Results: MC patients exhibited increased early supernormality, but this was prevented by treatment with sodium channel blockers. After multiple conditioning stimuli, late supernormality was enhanced in all MC patients, indicating delayed repolarization. These abnormalities were similar between the MC subtypes, but recessive patients showed a greater drop in amplitude during repetitive stimulation. Conclusions: MVRCs indicate that chloride conductance only becomes important when muscle fibers are depolarized. The differential responses to repetitive stimulation suggest that, in dominant MC, the affected chloride channels are activated by strong depolarization, consistent with a positive shift of the CLC‐1 activation curve. Muscle Nerve 49: 845–857, 2014Keywords
This publication has 33 references indexed in Scilit:
- Refined exercise testing can aid dna‐based diagnosis in muscle channelopathiesAnnals of Neurology, 2011
- Chloride currents from the transverse tubular system in adult mammalian skeletal muscle fibersJournal of General Physiology, 2010
- Velocity recovery cycles of human muscle action potentials in chronic renal failureClinical Neurophysiology, 2010
- The non-dystrophic myotonias: molecular pathogenesis, diagnosis and treatmentBrain, 2009
- Velocity recovery cycles of human muscle action potentials and their sensitivity to ischemiaMuscle & Nerve, 2009
- Cytoplasmic ATP-sensing Domains Regulate Gating of Skeletal Muscle ClC-1 Chloride ChannelsJournal of Biological Chemistry, 2005
- Decrement of compound muscle action potential is related to mutation type in myotonia congenitaMuscle & Nerve, 2003
- Resting Skeletal Muscle Membrane Potential as an Index of Uremic ToxicityJournal of Clinical Investigation, 1979
- Characteristics of the chloride conductance in muscle fibers of the rat diaphragm.Journal of General Physiology, 1977
- Muscle weakness after rest in myotonic disorders: an electrophysiological studyJournal of Neurology, Neurosurgery & Psychiatry, 1974