Focal cerebral ischemia in rats: effects of induced hypertension, during reperfusion, on CBF

The effect of phenylephrine-induced hypertension on CBF was investigated after 120 min of middle cerebral artery occlusion in rats. Blood pressure was manipulated by one of the following schedules during a 90-min period of reperfusion: 90/NORM, 90 min of normotensive reperfusion; 90/HTN, 90 min of hypertensive reperfusion (MABP increased by 30 mm Hg); or 15/HTN, the 90-min period of reperfusion was divided into 30 min of normotension, followed by 15 min of hypertension and 45 min of normotension. At the end of reperfusion, 100 microCi kg-1 of [14C]iodoantipyrine was given and an autoradiographic analysis of CBF performed. In the coronal brain section at the center of middle cerebral artery distribution, the area (percentage of hemisphere, mean +/- SD) with a CBF of 0-20 or 21-40 ml 100 g-1 min-1 was less (p less than 0.05) in the 15/HTN group (1 +/- 2 and 5 +/- 3%, respectively) versus the 90/HTN group (12 +/- 4 and 10 +/- 4%), which was in turn less than in the 90/NORM group (18 +/- 5 and 22 +/- 6%). These data are consistent with the hypothesis that during reperfusion a short interval of hypertension effectively augments CBF via an abrupt opening of collapsed vessels and that a more sustained interval of hypertension conveys no added benefit.