Postganglionic sympathetic activity with correlation to heart rhythm and central cortical rhythms

Area of Science:

• Neuroscience
• Cardiovascular Physiology

Background:

• The regulation of renal sympathetic nerve activity (RSNA) is crucial for maintaining cardiovascular homeostasis.
• Understanding the central neural networks involved in sympathetic outflow is essential for managing conditions like hypertension.

Purpose of the Study:

• To investigate the central mechanisms generating rhythms in renal sympathetic nerve activity.
• To explore the relationship between electroencephalogram (EEG) rhythms and sympathetic nerve activity in anesthetized dogs.

Main Methods:

• Recording of renal sympathetic nerve activity, electrocardiogram (ECG), and parieto-occipital EEG in chloralose-anesthetized dogs with sectioned carotid sinus nerves.
• Analysis of autocovariance functions and power spectra to identify rhythmic patterns.
• Vagal nerve cooling to modulate autonomic activity.

Main Results:

• Vagal nerve cooling induced rhythms in integrated RSNA that correlated with delta-theta rhythms in the EEG.
• These EEG-associated rhythms were also observed with intact vagus nerves, though a cardiac rhythm was dominant.
• Blood pressure-dependent neurons in the lower brainstem reticular formation exhibited both cardiac and central cortical rhythms.

Conclusions:

• Central cortical rhythms, particularly delta-theta activity, influence renal sympathetic nerve activity.
• Blood pressure-sensitive neurons in the brainstem reticular formation may play a role in generating sympathetic tone through integrated cardiac and cortical rhythms.