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 ch anges of the arteries of the circle of Willis on cerebral blood flow ( CBF) and metabolism in young spontaneously hypertensive rats (SHR). CB F 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 enz ymatic methods at a one-hour BCO. The internal diameters of the main a rteries of the circle of Willis were estimated morphologically. With i ncrease in age, systemic arterial pressure at rest was significantly r aised, while cortical CBF tended to decrease and calculated cerebral v ascular resistance increased. During BCO, CBF and supratentorial metab olism (adenosine triphosphate and lactate/pyruvate ratio) tended to be better presented in two-month-old rats as compared with those in one- or three-month-old rats. The internal diameter of the posterior commu nicating artery (PcomA) was significantly smaller in the one-month-old group than in the other groups, while the diameter of the internal ca rotid artery was significantly smaller in rats aged three months than those in rats aged one or two months. It is indicated that cortical CB F reduction and impairment of supratentorial metabolism following occl usion of carotid arteries, at least in part, depend on the morphologic changes of the arteries of the circle of Willis associated with age a nd development of hypertension in young SHR.