Spinal pathways mediating respiratory influences on sympathetic nerves

Area of Science:

• Neuroscience
• Cardiovascular Physiology
• Respiratory Physiology

Background:

• Sympathetic nerve activity is modulated by respiratory rhythms, influencing cardiovascular function.
• The precise spinal pathways responsible for this respiratory modulation of sympathetic activity remain incompletely understood.

Purpose of the Study:

• To determine the location of spinal cord pathways mediating the respiratory modulation of sympathetic nerve activity.
• To investigate the role of specific spinal cord tracts in integrating respiratory and sympathetic signals.

Main Methods:

• Recorded sympathetic, phrenic, and intercostal nerve activities in anesthetized, vagotomized, paralyzed cats.
• Utilized ventral and dorsolateral funiculus (DLF) lesions at the C6-C7 spinal cord level.
• Assessed respiratory modulation of sympathetic activity using respiration-triggered computer summation and baroreceptor reflex responses via carotid occlusion.

Main Results:

• Ventral spinal cord hemisections did not significantly affect respiratory modulation of sympathetic activity or baroreceptor responses.
• Bilateral DLF lesions abolished both respiratory modulation of sympathetic activity and baroreceptor reflex responses.
• Unilateral DLF pathway disruption suggested spinal-level decussations of these pathways.

Conclusions:

• Descending dorsolateral funiculus (DLF) pathways, with decussations at the spinal level, are critical for mediating the respiratory modulation of sympathetic nerve activity.
• These DLF pathways are essential for integrating respiratory signals with sympathetic outflow and baroreceptor reflex control.