Effects of angiotensin II on blood flow to choroid plexus.

The choroid plexus contains receptors for angiotensin II and a very high concentration of angiotensin-converting enzyme. The goal of this study was to test the hypothesis that angiotensin II decreases blood flow to the choroid plexus. In rabbits anesthetized with chloralose, blood flow (microspheres) to the choroid plexus was 438 +/- 46 (mean +/- SE) ml.min-1.100 g-1 under control conditions. Angiotensin II (10, 30, and 100 ng.kg-1.min-1 iv) decreased blood flow to the choroid plexus by 12 +/- 8, 39 +/- 7, and 57 +/- 5%, respectively, with aortic pressure maintained at control levels. Cerebral blood flow was not affected by angiotensin II. Blood flow to the kidney decreased by 15 +/- 7, 30 +/- 3, and 49 +/- 5%, respectively, during infusion of the three doses of angiotensin II. The angiotensin II antagonist saralasin (1 micrograms.kg-1.min-1 iv) did not affect blood flow to the cerebrum or the choroid plexus under control conditions. Saralasin blocked the vasoconstrictor effect of angiotensin II on the choroid plexus and the kidney. Thus circulating angiotensin II has important and parallel effects on blood flow to the choroid plexus and kidney that are mediated by angiotensin II receptors. We speculate that circulating and perhaps locally produced angiotensin II may play an important role in regulation of blood flow to the choroid plexus.