Effects of vasoactive stimuli on blood flow to choroid plexus

The goal of this study was to examine effects of vasoactive stimuli on blood flow to choroid plexus. We used microspheres to measure blood flow to choroid plexus and cerebrum in anesthetized dogs and rabbits. A critical assumption of the microsphere method is that microspheres do not pass through arteriovenous shunts. Blood flow values obtained with simultaneous injection of 15- and 50-micron microspheres were similar, which suggests that shunting of 15-micron microspheres was minimal. Blood flow to choroid plexus under control conditions was 287 +/- 26 (means +/- SE) ml.min-1.100 g-1 in dogs and 385 +/- 73 ml.min-1.100 g-1 in rabbits. Consecutive measurements under control conditions indicated that values for blood flow are reproducible. Adenosine (5 microM.kg-1. min-1 iv) did not alter blood flow to cerebrum but increased blood flow to choroid plexus two- to threefold in dogs and rabbits. Norepinephrine (0.5 micrograms.kg-1.min-1) and phenylephrine (25 micrograms.kg-1.min-1) did not affect blood flow to cerebrum but decreased blood flow to choroid plexus by approximately 50%. We suggest that 1) the microsphere method provides reproducible valid measurements of blood flow to the choroid plexus in dogs and rabbits and 2) vasoactive stimuli may have profoundly different effects on blood flow to choroid plexus and cerebrum.