High-salt diet elevates baroreceptor pressure thresholds in normal and Dahl rats

Area of Science:

• Cardiovascular Physiology
• Renal and Hypertension Research
• Neuroscience

Background:

• Dahl Salt Sensitive (DS) rats exhibit salt-induced hypertension.
• DS rats may have impaired baroreceptor afferents and baroreflexes.
• Baroreceptor function is crucial for blood pressure regulation.

Purpose of the Study:

• To investigate baroreceptor pressure- and mechano-transduction in DS, Dahl Resistant (DR), and Sprague-Dawley (SD) rats.
• To compare baroreceptor function under low- and high-salt diets.
• To determine if altered baroreceptor function contributes to salt sensitivity.

Main Methods:

• In vitro aortic arch-aortic nerve preparation used to study single baroreceptor units.
• Pressure ramps applied to assess pressure thresholds and sensitivities.
• Pressure-diameter relations used to convert pressure-based measures to mechanical strain equivalents.

Main Results:

• High-salt diet increased pressure thresholds in all rat groups.
• DS rats exhibited the highest pressure threshold, while DR rats had the lowest on a high-salt diet.
• Baroreceptor pressure sensitivities were lowest in DS rats and highest in DR rats on a low-salt diet.
• Differences in pressure thresholds were normalized when expressed as mechanical strain, suggesting mechanical transduction is intact.

Conclusions:

• Baroreceptors in DS and DR rats represent extremes of normal baroreceptor function.
• DS rats show reduced pressure responsiveness, while DR rats show increased responsiveness compared to SD rats.
• Altered baroreceptor pressure transduction, not mechanical properties, likely contributes to hypertension in DS rats.