Effect of High and Low Sodium Intake on Norepinephrine Turnover in the Cardiovascular Tissues and Brain Stem of the Rabbit

SUMMARY To assess the relationship between sympathetic nerve function and sodium intake, we ex-amined norepinephrine (NE) turnover in several cardiovascular tissues and the brain stem of rabbits main-tained for 3 weeks on high (86 mEq), normal (14 mEq), and low (0.2 mEq/day) sodium diet. None of the diets changed the blood pressure significantly. Plasma renin activity became high in the low sodium group and low in the high sodium group at the end of the treatment. NE turnover was measured from the rate of decline of tis-sue NE concentration after administration of a-methyl-p-tyrosine. Variation of sodium intake exerted op-posite effects on NE turnover in the periphery and in the central nervous system; increasing sodium intake caused an increase in NE turnover in the thoracic aorta, mesenteric vein, and left ventricle, and a decrease in the hypothalamus, midbrain, and pons medulla. But in the mesenteric artery and abdominal aorta it was not affected by dietary sodium manipulation. The results show the varying influence of sodium balance on the cen-tral and peripheral noradrenergic neuron activity. (Hypertension 4: 294-298, 1982) KEY WORDS • norepinephrine turnover • cardiovascular tissues • brain stem • dietary sodium SODIUM intake and the sympathetic nerves aremajor factors implicated in hypertension.There are mutual interactions between these two factors; sodium excretion is modified by the ac-tivity of sympathetic nerves,1- * and sympathetic nerv