Key result
Dietary sodium restriction in rats increased basal parasympathetic tone, enhanced heart rate responses to sympathetic activation, and elevated intrinsic cardiac rate.
Why the study?
Does dietary sodium restriction affect heart rate control in male Wistar rats?
Does dietary sodium restriction affect heart rate control in male Wistar rats?
In a rat model, dietary sodium restriction alters autonomic control of heart rate by increasing basal parasympathetic tone, enhancing sympathetic responsiveness, and elevating intrinsic cardiac rate.
Should not change sodium restriction practices; leaves open autonomic effects in humans.
The effects of dietary sodium restriction on heart rate control were evaluated in male Wistar rats maintained for 4 wk on a low- (22 meq/kg diet) or standard (141 meq/kg diet) sodium diet. In conscious low-sodium rats, atropine produced heart rate increases greater than in standard sodium animals, indicating that basal parasympathetic tone was elevated. Sodium restriction did not affect basal sympathetic tone, since similar reductions in heart rate were produced by propranolol in both dietary groups. However, sympathetically mediated tachycardic responses to sodium nitroprusside were augmented in low-sodium rats. This enhancement of sympathetic function was also observed in low-sodium animals after pithing. The increases in heart rate produced by spinal sympathetic stimulation were significantly accentuated; whereas, responses to norepinephrine were not affected by the diets. This finding is in agreement with the observation that the chronotropic responses elicited by isoproterenol in isolated atria were not altered. When neuronal influences on heart rate were blocked by combined administration of atropine and propranolol or chlorisondamine in conscious rats, the underlying intrinsic cardiac rate was found to be significantly higher in low-sodium rats. In summary, the present study identifies three effects of sodium restriction on heart rate control in the rat: 1) basal parasympathetic tone is increased, 2) heart rate responses to sympathetic activation are enhanced, and 3) the intrinsic cardiac rate is elevated.
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Bush et al. (1983) studied Heart rate control. Dietary sodium restriction vs. Standard sodium diet (141 meq/kg diet) was evaluated on Heart rate control (parasympathetic tone, sympathetic response, intrinsic rate). Dietary sodium restriction in rats increased basal parasympathetic tone, enhanced heart rate responses to sympathetic activation, and elevated intrinsic cardiac rate.