Repetitive action potentials induced in chloride-free solution: Effect of denervation |
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| Authors: | Basilio Aristidis Kotsias |
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| Institution: | 1. Centro de Investigaciones Medicas A. Einstein, Donato Alvarez 3150, 1427 Buenos Aires, Argentina;2. Instituto de Investigaciones Médicas, Donato Alvarez 3150, 1427 Buenos Aires, Argentina;1. Department of Neurology, Kyoto University Graduate School of Medicine, Japan;2. Department of Clinical Neuroscience and Therapeutics, Hiroshima University Graduate School of Biomedical and Health Sciences, Japan;3. Department of Clinical Laboratory Medicine, Kyoto University Graduate School of Medicine, Japan;4. Department of Epilepsy, Movement Disorders and Physiology, Kyoto University Graduate School of Medicine, Japan;1. Faculty of Medicine and Health, Central Clinical School, Brain and Mind Centre, University of Sydney, Sydney 2006, Australia;2. Central Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia;3. Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA;4. Natus Medical Inc, Middleton, Wisconsin, USA and Medical College of Wisconsin, Milwaukee, WI, USA;5. Neuromuscular Diseases Unit/ALS Clinic, Kantonsspital, St. Gallen, Switzerland;6. Department of Neurology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan;7. Division of Neurology, Department of Medicine, University of Malaya, Kuala Lumpur 50603, Malaysia;8. Newcastle University Translational and Clinical Research Institute (NUTCRI), Newcastle University., Newcastle Upon Tyne, United Kingdom;9. Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, WC1N 3BG, London, United Kingdom;10. Department of Clinical Neurophysiology, Aarhus University Hospital and Department of Clinical Medicine, Aarhus University, Aarhus, Denmark;1. Department of Neurology, Medical College of Wisconsin, Milwaukee, WI USA;2. Instituto de Medicina Molecular and Institute of Physiology, Centro de Estudos Egas Moniz, Faculty of Medicine, University of Lisbon, Portugal;3. Department of Neurosciences and Mental Health, CHULN-Hospital de Santa Maria, Lisbon, Portugal;4. Barts and the London School of Medicine, Queen Mary University of London, London UK;5. Department of Medical Sciences, Uppsala University, Uppsala, Sweden;6. Natus Medical Inc., Hopewell Junction, NY, USA |
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| Abstract: | Isometric mechanical activity and action potentials registered with intracellular microelectrodes were studied in innervated and denervated fibers of the soleus muscle of the rat in normal and chloride-free solutions. The chloride-free solution promoted in both innervated and denervated fibers an increment in the resting membrane potential. The innervated muscles showed long mechanical relaxation and repetitive action potentials after a single depolarizing pulse. On the contrary, denervated muscles were resistant to show mechanical and electrical changes in the chloride-free medium. Spontaneous and evoked action potentials from innervated muscle fibers were abolished by tetrodotoxin. The evoked action potentials generated in denervated fibers had a slower time course and were resistant to tetrodotoxin. After 7 to 10 days of denervation the input resistance was increased by about 30%. Substitution of chloride with sulfate resulted in a 150% increase in input resistance of innervated muscle fibers and 80% in denervated preparations. Alterations in the ionic conductances, a decrease in the maximum rate of rise of the action potentials, and changes in the sodium current kinetics could be the main factors for the absence of repetitive action potentials in denervated fibers exposed to the chloride-free medium. |
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