Effects of an Angiotensin-Converting Enzyme Inhibitor and a b-Blocker on Cerebral Arterioles in Rats

We examined the effects of an angiotensin-converting enzyme inhibitor, perindopril, and a b-blocker, propranolol, on cerebral arterioles in stroke-prone spontaneously hypertensive rats (SHRSP). The structure and mechanics of cerebral arterioles were examined in untreated Wistar-Kyoto rats (WKY) and SHRSP that were untreated or treated for 3 months with a high (2 mg/kg per day) or a low (0.3 mg/kg per day) dose of perindopril or propranolol (250 mg/kg per day) alone or in combination with the low dose of perindopril. We measured pressure, external diameter, and cross-sectional area of the vessel wall (CSA) in maximally dilated (with EDTA) cerebral arterioles. Treatment of SHRSP with the high dose of perindopril or the combination of propranolol and the low dose of perindopril normalized cerebral arteriolar mean pressure (5061 [mean6SEM] and 4362 mm Hg vs 5061 mm Hg in WKY and 9463 mm Hg in untreated SHRSP; P,0.05), pulse pressure (1561 and 1661 mm Hg vs 1361 mm Hg in WKY and 3561 mm Hg in untreated SHRSP; P,0.05), and CSA (1103653 and 1099651 mm, respectively, vs 1057649 mm in WKY and 1281662 mm in untreated SHRSP; P,0.05). In contrast, treatment of SHRSP with the low dose of perindopril or propranolol alone did not normalize arteriolar pulse pressure (2461 and 2161 mm Hg) and failed to prevent increases in CSA (1282677 and 1267694 mm). Treatment with either dose of perindopril or the combination of propranolol and perindopril significantly increased external diameter in cerebral arterioles of SHRSP (9963, 10362, and 9863 mm vs 8762 mm in untreated SHRSP; P,0.05), whereas propranolol alone did not (9463 mm; P.0.05). These findings suggest that effects of angiotensin-converting enzyme inhibitors on cerebral arteriolar hypertrophy in SHRSP may depend primarily on their effects on arterial pressure, particularly pulse pressure, whereas their effects on cerebral arteriolar remodeling (defined as a reduction in external diameter) may be pressure independent. (Hypertension. 1999;33:856-861.)