Functional Studies of the Cerebral Circulation

Angiotensin II (Ang II) is an endogenous peptide that has a wide spectrum of physiological functions, including the regulation of hemodynamics and blood volume (1); growth, hypertrophy, and remodeling in the cardiovascular system (1 ,2 ); regulation of microvessel density (3 ,4 ), and modulation of vascular tone (3 ,5 ). Ang II is widely known as a potent vasoconstrictor, but a number of studies have demonstrated that it can have vasodilator effects as well (3 ,5 ). The recent identification of distinct AT₁ and AT₂ angiotensin receptor subtypes raises additional questions regarding the actions of Ang II on the vascu-lature, particularly in regard to the role of these receptors in overall cardiovascular regulation (1 ,2 ).