Effect of sodium depletion on the release of [3H]norepinephrine from central and peripheral tissue of Wistar-Kyoto and spontaneously hypertensive rats.

To study the relationship between sodium intake, the sympathetic nervous system, and hypertension, we studied the effects of a 7-9 day dietary restriction of sodium in three different ages of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Field-stimulated [3H]norepinephrine ( [3H]NE) release was measured in portal vein, anterior hypothalamus, and the A2 region of the nucleus tractus solitarius (NTS) of 5- to 6-, 10- to 11-, and 28- to 30- week-old SHR and age-matched WKY. A low-sodium diet (0.05% Na+, control 0.5% Na+) significantly lowered stimulated [3H]NE release from portal vein and anterior hypothalamus in SHR and WKY at all three ages. However, release from the A2 region was not altered by sodium restriction. The results of the present study suggest that lowered dietary sodium can selectively alter norepinephrine release in both the peripheral and central sympathetic nervous system of SHR and WKY. The results also suggest that the SHR at 5-6 weeks are more sensitive to altered dietary sodium than are age-matched WKY.