Brief bilateral carotid artery ligation in adult spontaneously hypertensive rats (SHR) induced locomotor hyperactivity and lesions of the CA-, region of the hippocampus but had no effect in Wistar normotensive rats. This result suggests that high blood pressure amplifies the consequences of cerebral ischaemia. Treatment for 7 weeks with the calcium entry-blocker isradipine (5 mg/kg per day, subcutaneously) normalized blood pressure and attenuated the behavioural and histological consequences of cerebral ischaemia. Chronic treatment with hydralazine (25 mg/kg per day, subcutaneously) also normalized blood pressure but afforded no protection against the consequences of cerebral ischaemia. This suggests that the protective effect of antihypertensive treatment depends not only on the blood pressure—Slowering action but may also be linked to the mechanism of action of the drug used