Rhythmicity in single fiber postganglionic activity supplying the rat tail

Area of Science:

• Neuroscience
• Physiology
• Autonomic Nervous System Research

Background:

• The temporal patterning of sympathetic vasoconstrictor activity is crucial for neurovascular transmission.
• Understanding the rhythmicity of sympathetic nerve activity is key to comprehending its role in physiological regulation.

Purpose of the Study:

• To analyze the rhythmic firing patterns of postganglionic sympathetic fibers innervating the rat tail under normocapnic conditions.
• To investigate the influence of cardiac, respiratory, and artificial ventilation rhythms on sympathetic vasoconstrictor activity.

Main Methods:

• Recorded single-fiber postganglionic sympathetic activity from the ventral collector nerve in anesthetized, vagotomized Wistar rats.
• Utilized electrocardiogram synchronization, phrenic nerve activity, and tracheal pressure monitoring to assess rhythmicity.
• Employed spectral analysis and autocorrelation to identify dominant rhythmic patterns distinct from respiration.

Main Results:

• Cardiac rhythmicity in sympathetic activity was weak (46.2%).
• The central respiratory cycle was the dominant rhythm in most analyzed fibers (37/51 single fibers), characterized by inhibition during inspiration and activation during expiration.
• A significant portion of fibers also showed modulation related to artificial ventilation (21/37) or pump-related activity (11/51), with respiratory modulation being subordinate in the latter group.

Conclusions:

• Ongoing sympathetic postganglionic neuron activity supplying the rat tail is predominantly modulated by the central respiratory rhythm generator.
• Changes in respiratory drive can alter rat tail perfusion and thus affect thermoregulation.
• Reflex modulation linked to artificial ventilation, potentially via baroreceptor activity changes, is also a significant source of rhythmicity, independent of vagal afferents.