Sympathetic neural activation: an ordered affair.

Area of Science:

• Neuroscience
• Physiology

Background:

• The recruitment pattern of postganglionic sympathetic neurons during stress is not fully understood.
• Investigating this pattern is crucial for understanding vasomotor control and neuronal plasticity.

Purpose of the Study:

• To determine if sympathetic vasomotor neuron activation during stress adheres to the size principle of recruitment.
• To analyze the relationship between action potential characteristics and neuronal recruitment.

Main Methods:

• Collected multi-unit postganglionic sympathetic activity from the fibular nerve in five male subjects during rest and stress (end-inspiratory apneas).
• Utilized advanced action potential detection and analysis techniques to measure burst size, action potential number, and amplitude.
• Calculated action potential conduction velocities based on detected latencies.

Main Results:

• Elevated sympathetic stress significantly augmented sympathetic burst size compared to baseline.
• Increased burst size correlated directly with the number and amplitude of action potentials.
• Larger neurons accounted for approximately 74% of the increase in detected action potentials, indicating recruitment by size.
• Action potential conduction velocity increased with action potential size, consistent with larger axon diameters.

Conclusions:

• The findings suggest that postganglionic sympathetic vasomotor neurons are recruited in an ordered manner based on neuronal size, similar to the size principle.
• This ordered recruitment influences vasomotor control during stress and may have implications for sympathetic neuronal properties in health and disease.