Angiotensin facilitation of 3H-norepinephrine release in central tissue of spontaneously hypertensive rats but not in Wistar-Kyoto rats: effects of sodium depletion.

The purpose of the present study was to determine the ability of angiotensin II to facilitate the field stimulation-induced release of 3H-norepinephrine from brain areas of three ages of normal or salt-restricted spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Angiotensin II facilitated the stimulation-induced release of 3H-norepinephrine from the anterior hypothalamus of 5-6, 10-11, and 28-30 week-old SHR but not age-matched WKY. Angiotensin II failed to alter 3H-norepinephrine release in the A2 region of the nucleus tractus solitarius of either SHR or WKY, at all ages tested. Placement of rats on a sodium-restricted diet for 7 days abolished the facilitation of induced 3H-norepinephrine release by angiotensin, seen in the SHR at 5-6 and 10-11 weeks, but not that at 28-30 weeks. These results suggest that angiotensin II can facilitate noradrenergic release in the anterior hypothalamus of SHR but not WKY. This facilitation by angiotensin II in SHR can be altered by placement of the rats (5-6, 10-11 week-old) on a sodium-restricted diet.