Captopril improves cerebrovascular structure and function in old hypertensive rats

1 We examined the effects of an angiotensin-converting enzyme inhibitor (ACEI), captopril, on cerebral arterioles in young and old spontaneously hypertensive rats (SHR). 2 Animals were anesthetized with sodium pentobarbitone (60 mg kg(-1) day(-1)). We measured cerebral blood flow (CBF, arbitrary units) and cerebral arteriolar internal diameter ( ID, mm) prior to and during stepwise hypotension (SH) in 6- (WKY-6) and 15-month-old (WKY-15) Wistar Kyoto rats and in age-matched SHR that were untreated (SHR-6 and SHR-15) or treated for 3 months with captopril (SHR-6C, 105+/-2 mg kg(-1) day(-1) and SHR-15C, 94+/-1 mg kg(-1) day(-1)). ID and cross-sectional area of the vessel wall (CSA) were measured in deactivated ( EDTA) cerebral arterioles during a second SH. 3 Captopril decreased the lower limit of CBF autoregulation (61+/-6 in SHR-6C and 51+/-2 in SHR-15C versus 52+/-6 in WKY-6 and 62+/-7 in WKY-15 and 83+/-14 mm Hg in SHR-6 and 120+/-19 mm Hg in SHR-15; P<0.05) and CSA (510 +/- 21 in SHR-6C and 585 +/- 25 in SHR-15C versus 529 +/- 12 in WKY-6 and 549 +/- 20 in WKY-15 and 644 +/- 38 mm Hg in SHR-6 and 704 +/- 38 mm Hg in SHR-15; P<0.05). 4 Captopril increased cerebral arteriolar external diameter of SHR (105+/-5 in SHR-6C and 94+/-4 in SHR-15C versus 12578 in WKY-6 and 10873 in WKY-15 and 83+/-2 mm Hg in SHR-6 and 80+/-2 mm Hg in SHR-15 for a pial arteriolar pressure step of 35-39 mm Hg; P<0.05). Captopril attenuated increases in cerebral arteriolar distensibility in young SHR. 5 Thus, ACEIs attenuate eutrophic and hypertrophic inward remodeling of cerebral arterioles in young and old SHR, thus decreasing the lower limit of CBF autoregulation.