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Absence of fibrillation after muscle injury
Abstract:
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.
Insights
Fibrillation potentials, abnormal muscle electrical activity, do not arise from segmental necrosis in muscle fibers. Surgical denervation, however, reliably induces these potentials, impacting understanding of myopathic disorders.
Area of Science:
- Neuroscience
- Muscle Physiology
- Pathology
Background:
- Fibrillation potentials are spontaneous electrical activities in muscle fibers.
- Their occurrence is typically associated with denervation.
- The role of segmental necrosis in inducing fibrillation potentials was previously unclear.
Purpose of the Study:
- To investigate whether segmental necrosis of muscle fibers can lead to fibrillation potentials.
- To compare fibrillation activity resulting from necrosis versus surgical denervation.
Main Methods:
- Focal necrotic lesions were induced in rat semitendinosus muscles via crushing, ligating, or cutting fibers.
- Microscopic examination and intracellular/extracellular electrode recordings were performed.
- Surgical denervation was performed on rat semitendinosus muscles for comparison.
- Human brachioradialis muscle after myotomy was also examined.
Main Results:
- Fibrillation potentials were absent or extremely infrequent in muscles with induced segmental necrosis.
- Fibrillation potentials were also absent in a human muscle after myotomy.
- Surgical denervation of rat muscles induced fibrillation activity within 3 days, affecting approximately 50% of fibers.
Conclusions:
- Segmental necrosis of muscle fibers does not appear to cause fibrillation potentials.
- Surgical denervation is a potent inducer of fibrillation potentials.
- These findings refine the understanding of fibrillation potential pathogenesis in myopathic disorders.