Functional changes of the peripheral nervous system with aging in the mouse

Area of Science:

• Neuroscience
• Gerontology
• Physiology

Background:

• Peripheral nerve function and target organ interactions are crucial for maintaining physiological homeostasis.
• Aging is associated with progressive declines in various bodily functions, including neurological and motor capabilities.
• Understanding age-related changes in the nervous system is vital for developing interventions to improve quality of life in older populations.

Purpose of the Study:

• To investigate the influence of aging on peripheral nerve function and associated target organ responses.
• To evaluate age-related alterations in sudomotor, motor, and sensory functions mediated by the sciatic nerve.
• To elucidate the differential impact of aging on nerve fibers of varying diameters.

Main Methods:

• Comparative analysis of six mouse groups aged 2, 6, 9, 12, 18, and 24 months.
• Assessment of sudomotor function using pilocarpine-induced sweat droplet analysis.
• Electrophysiological recordings and pinprick tests were employed to evaluate motor and sensory nerve function.

Main Results:

• The number of sweat glands remained stable, but sweat droplet size diminished in aged mice.
• Progressive decline in the amplitude of muscle and nerve action potentials was observed with age.
• Nerve conduction latencies initially decreased then increased, indicating age-related changes in nerve signal transmission.
• Sensory responses to pinprick remained consistent across all age groups, suggesting preservation of small nerve fibers.

Conclusions:

• Aging significantly impacts neurophysiological responses mediated by large diameter nerve fibers, affecting motor and sensory capabilities.
• Small diameter nerve fibers, responsible for certain sensory functions, appear to be preserved during the aging process.
• These findings highlight a differential vulnerability of peripheral nerve fiber types to aging, with implications for age-related functional decline.