Central alpha 2-adrenoceptor responsiveness in borderline hypertensive rats

Area of Science:

• Neuroscience
• Cardiovascular Physiology
• Renal Physiology

Background:

• Dietary salt (NaCl) intake influences blood pressure regulation.
• Central nervous system alpha 2-adrenoceptors modulate renal function and blood pressure.
• Spontaneously hypertensive rats (SHR) show increased alpha 2-adrenoceptor responsiveness with high salt, unlike Wistar-Kyoto (WKY) rats.

Purpose of the Study:

• To investigate if high dietary NaCl intake enhances central nervous system alpha 2-adrenoceptor responsiveness in borderline hypertensive rats (BHR).
• To determine if BHRs, offspring of SHR and WKY rats, inherit this salt-sensitive alpha 2-adrenoceptor characteristic.

Main Methods:

• BHRs were fed either 8% NaCl or 1% NaCl diets for six weeks.
• The alpha 2-adrenoceptor agonist, guanabenz, was administered intracerebroventricularly at graded doses (5, 25, 125 µg).
• Cardiovascular, renal sympathetic nerve activity, and diuretic responses were measured.

Main Results:

• High salt intake (8% NaCl) in BHRs augmented depressor, bradycardic, renal sympatho-inhibitory, and diuretic responses to guanabenz.
• These augmented responses indicate enhanced central alpha 2-adrenoceptor responsiveness.

Conclusions:

• Increased dietary NaCl intake enhances central nervous system alpha 2-adrenoceptor responsiveness in BHRs.
• This enhanced responsiveness appears to be genetically transmitted from the SHR parent and is unmasked by high salt intake in BHRs.