The aortic nerve-sympathetic reflex in the rat.

Area of Science:

• Neuroscience
• Cardiovascular Physiology
• Autonomic Nervous System Research

Background:

• The aortic nerve plays a crucial role in cardiovascular regulation.
• Understanding the specific fiber types within the aortic nerve is essential for elucidating baroreceptor reflex mechanisms.

Purpose of the Study:

• To investigate the effects of aortic nerve A- and C-fiber stimulation on renal and cardiac sympathetic nerve activity in rats.
• To determine if the rat's aortic nerve contains functionally active non-barosensory afferents.

Main Methods:

• Electrophysiological recordings of renal and cardiac sympathetic nerve activity in anesthetized Sprague-Dawley rats.
• Selective stimulation of aortic nerve A- and C-fiber groups.
• Comparison with stimulation of the superior laryngeal nerve.

Main Results:

• Activation of aortic nerve A- and C-fibers consistently inhibited renal and cardiac sympathetic nerve activity.
• No excitatory component, indicative of non-barosensory afferents, was observed.
• C-fiber stimulation produced a more potent and sustained sympatho-inhibitory effect than A-fibers, effective at low frequencies (2 Hz).

Conclusions:

• The rat's aortic nerve primarily contains barosensory afferents, with limited functionally active non-barosensory afferents.
• Aortic nerve stimulation provides a valuable tool for selectively activating central neural structures involved in baroreceptor reflexes.
• The sympatho-inhibitory responses elicited by aortic nerve stimulation are homologous to those observed in rabbits and cats.