Comparison of norepinephrine release in hypertensive rats: I. Hypothalamic and brainstem tissues.

Stimulation induced 3H-norepinephrine release was measured in hypothalamus and brainstem of spontaneously hypertensive (SHR) and normotensive (WKY) rats. Age dependent changes in 3H-norepinephrine release were shown to occur in the anterior and posterior hypothalamus and the A2 region of the nucleus tractus solitarius (NTS). In an attempt to determine whether these changes in 3H-transmitter release were causal or merely secondary to the increase in blood pressure, similar release studies were carried out in DOCA-salt and one kidney-one clip hypertensive animals with similar levels of systolic blood pressure. The changes in stimulus-induced 3H-norepinephrine release seen in the SHR were not observed in the other two models of hypertension, suggesting that one: they were not secondary to an increase in systolic blood pressure; and two that the changes observed in the SHR may possibly play a role in the development and/or maintenance of the hypertension.