EFFECTS OF LONG-ACTING ANGIOTENSIN-CONVERTING ENZYME-INHIBITOR, IMIDAPRIL, ON THE LOWER LIMIT OF CEREBRAL BLOOD-FLOW AUTOREGULATION IN HYPERTENSIVE RATS

The objective of the present study was to examine the effects of a lon g-acting angiotensin converting enzyme inhibitor, imidapril 3-{(2S)-2- [N-(1S)-1-ethoxycarbonyl-3-phenylpropyl) amino] propionyl}-2-oxoimidaz olidine-4-carboxylic acid hydrochloride), for 7 days on the cerebral b lood flow autoregulatory response to hypotension in hypertensive rats. We measured the cerebral blood flow at rest and during hemorrhagic hy potension, using laser-Doppler flowmetry. At the same time, the absolu te baseline cerebral blood flow values in the parietal cortex were qua ntified with the hydrogen clearance method. After administration of im idapril at a dose of 5 mg/kg/day for 7 days, the resting value of mean arterial blood pressure was significantly decreased by 25 mm Hg(P < 0 .001), cerebral vascular resistance was lowered by 14.4% (P < 0.05) an d the lower limit of cerebral blood flow autoregulation was shifted to a lower level, 106 +/- 11 mm Hg (mean +/- S.D.), from 137 +/- 8 mm Hg in the control group (P < 0.001), while resting cerebral blood flow r emained unchanged. The present results demonstrated that imidapril pre serves cerebral blood flow and significantly shifts the lower limit of cerebral autoregulation towards lower blood pressure levels. (C) 1998 Elsevier Science B.V.