Cardiac volume receptor reflex in borderline hypertensive rats

Area of Science:

• Cardiovascular Physiology
• Renal Physiology
• Hypertension Research

Background:

• Borderline hypertensive rats (BHR) fed high salt diets develop hypertension.
• Increased dietary sodium chloride (NaCl) intake is linked to hypertension.
• Exaggerated natriuresis in BHR is associated with renal sympathetic nerve activity withdrawal.

Purpose of the Study:

• To investigate cardiac volume receptor reflex control of efferent renal sympathetic nerve activity.
• To compare these reflexes in BHR with normal versus high NaCl intake.
• To understand the role of these reflexes in salt-induced hypertension.

Main Methods:

• BHR were fed either 1% or 8% NaCl from 4 to 16 weeks of age.
• Measurements of right atrial pressure and efferent renal sympathetic nerve activity were taken.
• Volume expansion and vagal nerve stimulation were used in sinoaortic-denervated rats.

Main Results:

• Rats fed 8% NaCl were hypertensive (148 mmHg) compared to 1% NaCl rats (115 mmHg).
• High salt intake led to greater inhibition of renal sympathetic nerve activity during volume expansion.
• The gain of the volume receptor reflex was also significantly greater in high salt rats.

Conclusions:

• Cardiac volume receptor reflexes are altered in salt-induced hypertension in BHR.
• Exaggerated withdrawal of renal sympathetic nerve activity contributes to hypertension.
• These findings highlight the role of volume receptors in salt-sensitive hypertension.