Angiotensin II in the Brain and Brainstem of the Doca Salt Hypertensive Rat

We previously reported that immunoreactive angiotensin II (AII) containing nerve fibers and cell bodies were increased in the brain and brainstem of the spontaneously hypertensive (SH) rat compared with its normotensive control, the Wistar Kyoto (WKY) rat. Since earlier studies from other laboratories described the distribution of AII in normotensive Sprague Dawley rat brain, it was the intent of this investigation to examine the localization of AII in the only DOCA-salt hypertensive rat. We unilaterally nephrectomized Sprague Dawley rats and administered multiple subcutaneous injections of 30 mg/kg body weight of DOCA, with saline substituted for drinking water to significantly increase blood pressure. Using the peroxidase anti-peroxidase method for immunocytochemical localization of a tissue antigen, we characterized AII distribution and density in the brain and brainstem of DOCA-salt hypertensive rats. Positively stained cell bodies and fiber profiles were found in discrete anatomical subdivisions, including the limbic system, hypothalamus, basal ganglia, circumventricular organs, reticular formation and ependymal tissue immediately adjacent to the ventricles. These findings support the hypothesis that AII is widely distributed in discrete regions of the DOCA-salt hypertensive rat brain and brainstem, and that the distribution of AII is consistent with a potential functional significance in the regulation of cardiovascular activity and neuroendocrine function.