Hemodynamic regulation in SHR: investigation by spectral analysis

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Research
• Hypertension Etiology

Background:

• Hypertension in spontaneously hypertensive rats (SHR) is hypothesized to result from autonomic cardiovascular control imbalances.
• Understanding these imbalances is crucial for identifying early markers and mechanisms of hypertension.

Purpose of the Study:

• To investigate spontaneous fluctuations in heart rate (HR) and arterial blood pressure (ABP) in young SHR and normotensive Wistar-Kyoto (WKY) rats.
• To determine if differences in ABP fluctuations correlate with autonomic control and central nervous system activity.

Main Methods:

• Spectral analysis of continuous ABP and HR recordings in conscious, unrestrained rats (1-6 months old).
• Comparative analysis between SHR and WKY rat strains.
• Assessment of effects of anesthesia and spinalization on ABP fluctuations.
• Pharmacological evaluation using phentolamine to probe sympathetic activity.

Main Results:

• HR fluctuations were similar between SHR and WKY rats.
• ABP fluctuations in the low (vasomotor) frequency range were significantly reduced in SHR compared to WKY rats.
• Anesthesia and spinalization reduced strain differences in ABP fluctuations, suggesting a central nervous system origin.
• Phentolamine affected ABP fluctuations differently in SHR and WKY rats, indicating altered sympathetic drive.

Conclusions:

• Reduced ABP fluctuations in young SHR, despite normal HR fluctuations, suggest impaired sympathetic control of resistance vessels.
• These findings highlight potential early indicators of hypertension related to autonomic dysregulation.
• The central nervous system plays a significant role in the observed differences in cardiovascular control between SHR and WKY rats.