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Ca‐dependent slow action potentials in neuromuscular diseases
Author(s) -
Siri L. Nicola,
Dubrovsky A. L.,
Uchitel O. D.
Publication year - 1990
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041430325
Subject(s) - central core disease , myopathy , chemistry , skeletal muscle , amyotrophic lateral sclerosis , polymyositis , medicine , endocrinology , anatomy , calcium , disease , ryanodine receptor , ryr1
Slow Ca‐dependent action potentials were studied in skeletal muscle fibers from different Neuromuscular Diseases (NMD). Byopsies were obtained from: 3 my ‐ opathies [Fascioscapulohumeral Dystrophy (FSH) and Polymyositis (PM)], 6 patients with other diseases (CD) [Amyotrophic Lateral Sclerosis (ALS), Central Core Disease, Mitochondrial Myopathy, Polyneuritis (PN), von Eulenberg's Paramyotonia], and 8 normal control muscles. Experiments were carried out in muscle fibers under current‐clamp conditions. Membrane currents other than Ca ones were abolished or greatly diminished. Muscle fibers produced any of 3 types of responses, when stimulated by depolarizing pulses: fully developed Ca‐action potentials (CaAP), abortive non‐regenerative Ca responses (NrR), or only capacitive passive responses (WR). The 3 types of responses were not dependent on the basal conditions of the fibers. The frequency of observation of CaAPs was significantly higher in myopathic disease. In myopathies , 46% of the muscle fibers had CaAPs, while only 22% of fibers from CD and 15% of the fibers from normal muscles showed CaAPs. No differences were observed in the resting constants as well as in the CaAPs parameters between normal and diseased muscle fibers.