ABSTRACT
Due to the presence of the blood-brain barrier circulating angiotensin (Ang) II has no access to most brain areas.1-3 Thus, the brain renin-angiotensin system (RAS) is autonomous concerning the generation and action of Ang peptides in contrast to most other tissue-specific RASs. Nevertheless, circulating Ang II transmits effects inside the brain through areas lacking the blood-brain barrier.4 The brain RAS is involved in the modulation of cardiovascular and fluid-electrolyte homeostasis,4 by modulating the activity of the autonomic nervous system,5-7 the hypothalamic-pituitary axis, the release of vasopressin,8 and baroreflex sensitivity9 and stimulating thirst.10,11 Moreover, the local RAS influences higher brain functions, such as memory, cognition, stress, and addiction.12,13
Angiotensinogen Essential for a functional brain RAS is the presence of the only known precursor for Ang peptides, angiotensinogen (AOGEN), in the brain.14-16 It is found throughout the brain with highest levels in areas of homeostatic control such as hypothalamus and brain stem. Astrocytes represent the main cell type synthesizing AOGEN.17
