A diagrammatic sketch of the brain showing Ang-II-sensitive areas and inaccessible areas. In the brain, some areas (red), such as the subfornical organ (SFO), the organum vasculosum of the lamina terminals (OVLT), and the area postrema (AP), contain AT₁ receptors that are accessible to circulating Ang II. Other areas (blue), such as the supraoptic (SON) and the paraventricular nuclei (PVN) of the hypothalamus, the rostral (R) and caudal (C) ventrolateral medullae (VLM), and the nucleus tractus solitarii (NTS), also contain AT₁ receptors that cannot be reached by systemic Ang II owing to the blood-brain barrier. These regions are only accessible to Ang II synthesized locally in the brain.