Angiotensin facilitation of noradrenergic neurotransmission in central tissues of the rat: effects of sodium restriction.

This study investigated the ability of angiotensin II (Ang II) to facilitate the stimulation-induced release of [3H]norepinephrine [( 3H]NE) from two cardiovascular regulatory areas in normal and sodium-restricted rats. Ang II (10(-7) M) facilitated the field-stimulation-induced release of [3H]NE from the A2 area of the nucleus tractus solitarius but not from the anterior hypothalamus of Sprague-Dawley and Wistar rats. Placement of rats on a sodium-restricted diet abolished the facilitation of [3H]NE release due to Ang II. Captopril given during sodium restriction partially restored the facilitory effects of Ang II. In an effort to determine the interaction of Ang II and sodium reduction, the effects of chronic Ang II were studied. Seven-day intravenous Ang II infusions blocked the facilitory effect of Ang II on [3H]NE release in a manner similar to that seen with sodium restriction. These results suggest that low sodium diets may alter the facilitation of [3H]NE release by Ang II by interactions with the renin-angiotensin system.