Renin-angiotensin system in the central nervous system: focus on Huntington's disease.

The renin-angiotensin system (RAS) was originally conceived as a circulating hormonal system involved in the regulation of cardiovascular and renal homeostasis. With the discovery of local RAS components in diverse organs, including the brain, and related biologically active peptides, enzymes, and receptors, the understanding of the physiological and pathophysiological roles of RAS has changed significantly.