EFFECTS OF DIPYRIDAMOLE IN SPONTANEOUSLY HYPERTENSIVE RABBITS WITH DIFFUSE CHRONIC CEREBRAL-ISCHEMIA

The effect of intravenous dipyridamole (0.7 mg/kg) on cerebral blood f low (CBF), mean arterial blood pressure (MABP), heart rate, respiratio n rate, cerebral electrical activity, arterial blood gases, pH, and gl ucose was investigated in 14 normotensive and 14 stroke-prone spontane ously hypertensive anesthetized rabbits. CBF was measured by hydrogen and heat clearance. In both groups, MABP decreased (normotensive: - 24 mm Hg, hypertensive: - 47 mm Hg; ANOVA: P < 0.0001) and CBF increased (normotensive: + 59 ml/ 100 g/min, hypertensive: + 72 ml/100 g/min; A NOVA: P < 0.0002). CBF returned to the initial level 21 min later in h ypertensive than in normotensive rabbits. Changes in other parameters were insignificant. In additional experiments, 30 mg/kg theophylline e ntirely prevented the cerebral vasodilator and systemic hypotensive ef fects of dipyridamole in both normotensive and hypertensive rabbits. W e conclude that, in stroke-prone spontaneously hypertensive rabbits, t he longer-lasting and larger CBF increase in response to dipyridamole may be attributed to reversible functional changes in the cerebral vas culature resulting from hypertension.