Absence of fibrillation after muscle injury.

The possibility was examined that fibrillation potentials may occur in those parts of muscle fibers which become functionally denervated following segmental necrosis. Focal necrotic lesions were induced in rat semitendinosus muscles by crushing, ligating, or cutting muscle fibers. When the treated muscles were examined microscopically and recordings made with intracellular or extracellular electrodes, fibrillations were found to be either completely absent or extremely infrequent. Fibrillation potentials were also absent in the brachioradialis muscle of a human subject after myotomy. In contrast to these negative results, surgical denervation of the rat semitendinosus induced fibrillation activity within 3 days; when fully developed, fibrillations occurred in approximately one-half of the fibers at any time. The findings are considered to have significance for an understanding of the pathogenesis of those "myopathic" disorders in which fibrillations are found.