期刊
AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY
卷 285, 期 5, 页码 C1161-C1173出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpcell.00128.2003
关键词
myogenic regulatory factor; denervation; spinal cord isolation; bromodeoxyuridine
资金
- NINDS NIH HHS [NS 16333] Funding Source: Medline
- NATIONAL INSTITUTE OF NEUROLOGICAL DISORDERS AND STROKE [P01NS016333] Funding Source: NIH RePORTER
Electrical activity is thought to be the primary neural stimulus regulating muscle mass, expression of myogenic regulatory factor genes, and cellular activity within skeletal muscle. However, the relative contribution of neural influences that are activity-dependent and -independent in modulating these characteristics is unclear. Comparisons of denervation (no neural influence) and spinal cord isolation (SI, neural influence with minimal activity) after 3, 14, and 28 days of treatment were used to demonstrate whether there are neural influences on muscle that are activity independent. Furthermore, the effects of these manipulations were compared for a fast ankle extensor (medial gastrocnemius) and a fast ankle flexor (tibialis anterior). The mass of both muscles plateaued at similar to60% of control 2 wk after SI, whereas both muscles progressively atrophied to <25% of initial mass at this same time point after denervation. A rapid increase in myogenin and, to a lesser extent, MyoD mRNAs and proteins was observed in denervated and SI muscles: at the later time points, these myogenic regulatory factors remained elevated in denervated, but not in SI, muscles. This widespread neural activity-independent influence on MyoD and myogenin expression was observed in myonuclei and satellite cells and was not specific for fast or slow fiber phenotypes. Mitotic activity of satellite and connective tissue cells also was consistently lower in SI than in denervated muscles. These results demonstrate a neural effect independent of electrical activity that 1) helps preserve muscle mass, 2) regulates muscle-specific genes, and 3) potentially spares the satellite cell pool in inactive muscles.
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