Brain ischemia following bilateral carotid occlusion during development of hypertension in young spontaneously hypertensive rats--importance of morphologic changes of the arteries of the circle of Willis.

The present study was designed to examine the effect of morphologic changes of the arteries of the circle of Willis on cerebral blood flow (CBF) and metabolism in young spontaneously hypertensive rats (SHR). CBF in the parietal cortex was measured by the hydrogen clearance method before and during a one-hour bilateral carotid artery occlusion (BCO), and supratentorial brain metabolites were determined by standard enzymatic methods at a one-hour BCO. The internal diameters of the main arteries of the circle of Willis were estimated morphologically. With increase in age, systemic arterial pressure at rest was significantly raised, while cortical CBF tended to decrease and calculated cerebral vascular resistance increased. During BCO, CBF and supratentorial metabolism (adenosine triphosphate and lactate/pyruvate ratio) tended to be better preserved in two-month-old rats as compared with those in one- or three-month-old rats. The internal diameter of the posterior communicating artery (PcomA) was significantly smaller in the one-month-old group than in the other groups, while the diameter of the internal carotid artery was significantly smaller in rats aged three months than those in rats aged one or two months. It is indicated that cortical CBF reduction and impairment of supratentorial metabolism following occlusion of carotid arteries, at least in part, depend on the morphologic changes of the arteries of the circle of Willis associated with age and development of hypertension in young SHR.