The renin-angiotensin system in the central control of blood pressure.

The results of biochemical, immunohistochemical and autoradiographic studies led to the description of the endogenous brain angiotensin II system as a highly localized network of angiotensin II-containing cell bodies and fibres as well as characteristic sites with high angiotensin II-receptor density. The specific localization of this system predominantly within limbic, hypothalamic and brain stem structures that are known to be involved in central cardiovascular regulation and the control of volume homeostasis, suggests a possible functional role for brain angiotensin II in the control of these homeostatic functions. A role for brain angiotensin II in the central control of blood pressure is further supported by physiological and pharmacological experiments that demonstrate characteristic central angiotensin-induced cardiovascular responses. However, it should be kept in mind that the mechanisms mediating these responses (e.g. sympathetic activation, vasopressin release), as well as the exact functional role of endogenously synthesized angiotensin II in specific brain areas, are not yet completely understood. Pathophysiologically, there is evidence that an activated brain renin angiotensin system may participate in the development and maintenance of primary hypertension.