Effect of angiotensin converting enzyme inhibition by cilazapril on circulation and cerebral vasomotor response in monkey

Vascular renin-angiotensin system has been suggested to play an important role in cerebral vasoactivities. The aim of the present study was to examine the effect of inhibition of angiotensin converting enzyme by cilazapril on intra- and extracranial circulation, cerebral metabolism and its vasomotor responses. The study was performed on 14 monkeys (macaca fuscata). Internal carotid blood flow (ICBF), vertebral blood flow (VBF), external carotid blood flow (ECBF) and femoral blood flow (FBF) were continuously measured by electromagnetic flowmeters with simultaneous measurements of blood pressure, pulse rate and PeCO2. Cilazapril (3 mg/kg) was intravenously injected in order to inhibit angiotensin converting enzyme (ACE). Cerebral vasomotor responses were quantitatively tested by means of controlled changes in blood pressure, autoregulation index (Al : ΔCBF/ΔMABP, ml/min/mmHg) and controlled changes in PaCO2, chemical vasomotor index (CVI : ΔCBF/ΔPaCO2, ml/min/mmHg). 1) Blood pressure and pulse rate : Blood pressure showed a significant fall after ACE inhibition, but no significant change was observed in pulse rate. 2) Intra- and extracranial circulation : ICBF and VBF decreased significantly in parallel with ACE inhibition by cilazapril. However, ECBF and FBF increased temporally and then ECBF was significantly decreased but FBF showed no significant change following ACE inhibition. 3) Cerebral metabolism : No significant changes were obtained in CMRO2 between before and after ACE inhibition. 4) CBF autoregulation : AI to induced hypotension became significantly lower following ACE inhibition (p