Angiotensin n Receptors in the Solitary-Vagal Area of Hypertensive Rats

Angiotensin II (Ang II) has been proposed to be an endogenous neuromodulator of the baroreceptor reflex at the level of the brain stem solitary-vagal area. Elevated activity of the brain Ang II system has been implicated in the development and maintenance of hypertension in spontaneously hypertensive rats and deoxycorticosterone acetate-salt hypertensive rats. In the present study, we sought to determine if Ang II receptors in the solitary-vagal area exhibited altered binding kinetics in spontaneously hypertensive rats or deoxycorticosterone-salt hypertensive rats. Ang II receptors were examined by quantitative autoradio-graphic analysis of iodine-125-labeled [Sar'Jle'JAng II binding in the solitary-vagal area in six groups of animals: 1) spontaneously hypertensive rats, 2) nonnotensive Wistar-Kyoto rats, 3) uninephrectomized rats, 4) uninephrectomized rats with a 1 % solution of saline for drinking water, 5) uninephrectomized and deoxycorticosterone-treated rats, and 6) uninephrectomized and deoxycorticosterone-treated rats given a 1 % solution of saline for drinking water. Blood pressure was significantly elevated in the spontaneously hypertensive rats and deoxycorticosterone-salt rats relative to control animals. There was a significant decrease in the binding affinity (increased KB) for l2sI-[Sar1Jles]Ang II and a significant increase in the maximum binding density for '"I-ISar^Ile'jAng II in the solitary-vagal area of spontaneously hyperten-sive rats relative to Wistar-Kyoto rats. Deoxycorticosterone-salt rats also exhibited significantly higher £