Increased dietary salt intake enhances the exercise pressor reflex

Increased dietary salt in rats has been shown to sensitize central sympathetic circuits and enhance sympathetic responses to several stressors, including hyperinsulinemia, intracerebroventricular injection of angiotensin, and electrical stimulation of sciatic nerve afferents. These findings prompted...

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Bibliographic Details
Published in:American journal of physiology. Heart and circulatory physiology 2014-02, Vol.306 (3), p.H450-H454
Main Authors: Yamauchi, Katsuya, Tsuchimochi, Hirotsugu, Stone, Audrey J, Stocker, Sean D, Kaufman, Marc P
Format: Article
Language:English
Subjects:
ACE inhibitors
Animals
Blood Pressure
Hindlimb
Male
Muscle Contraction
Muscle, Skeletal - drug effects
Muscle, Skeletal - innervation
Muscle, Skeletal - physiology
Physical Exertion
Rapid Reports
Rats
Rats, Sprague-Dawley
Reflex
Rodents
Salt
Sodium Chloride, Dietary - pharmacology
Spinal Nerve Roots - drug effects
Spinal Nerve Roots - physiology
Vasomotor System - drug effects
Vasomotor System - physiology
Veins & arteries
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Summary:Increased dietary salt in rats has been shown to sensitize central sympathetic circuits and enhance sympathetic responses to several stressors, including hyperinsulinemia, intracerebroventricular injection of angiotensin, and electrical stimulation of sciatic nerve afferents. These findings prompted us to test the hypothesis that increased dietary salt enhanced the exercise pressor reflex. Male Sprague-Dawley rats were fed 0.1% (low) or 4.0% (high) NaCl chow for 2 to 3 wk. On the day of the experiment, the rats were decerebrated, and the hind limb muscles were statically contracted for 30 s by electrically stimulating the cut peripheral ends of the L4 and L5 ventral roots. We found that contraction produced a significantly greater increase in mean arterial pressure of rats fed 4.0% (n = 26) vs. 0.1% (n = 22) NaCl (24 ± 2 vs. 15 ± 2 mmHg, respectively; P < 0.05). Baseline mean arterial pressure was not different between groups (0.1%, 77 ± 4 vs. 4.0% NaCl, 80 ± 3 mmHg). Likewise, the tension time indexes were not different between the two groups (P = 0.42). Section of the L4 and L5 dorsal roots greatly attenuated both the pressor and cardioaccelerator responses to contraction in both groups of rats, an effect showing that the responses were reflex in origin. Finally, electrical stimulation of the lumbar sympathetic chain produced similar increases in mean arterial pressure and decreases in femoral arterial blood flow and conductance between rats fed 0.1% vs. 4.0% NaCl diets. We conclude that increased dietary salt enhances the exercise pressor reflex.
ISSN:0363-6135
1522-1539
DOI:10.1152/ajpheart.00813.2013