Increased Single-Fiber Jitter Level Is Associated With Reduction in Motor Function With Aging.

Area of Science:

• Neurobiology
• Gerontology
• Skeletal Muscle Physiology

Background:

• Age-associated skeletal muscle weakness contributes to mortality and morbidity.
• Previous research indicated axonal degeneration and neuromuscular junction denervation in aging muscles.
• The neurobiology underlying age-related muscle weakness remains poorly understood.

Purpose of the Study:

• To investigate the relationship between impaired neuromuscular transmission and age-associated muscle weakness.
• To evaluate electrophysiological measures of neuromuscular function in aging mice.

Main Methods:

• Compared electrophysiological measures (single-fiber jitter, compound motor action potential) in young and old mice.
• Correlated electrophysiological data with physical performance tests (grip strength, standing/walking time, treadmill performance).

Main Results:

• Single-fiber jitter, a measure of neuromuscular junction transmission, was significantly increased in older mice.
• Compound motor action potential showed no age-related differences.
• Jitter correlated with standing activity, but not other physical performance measures.

Conclusions:

• Increased single-fiber jitter reflects impaired neuromuscular transmission with aging.
• Impaired neuromuscular transmission is linked to the decline in motor function observed in aging.