Choroid plexus blood flow in the sheep

Choroid plexus blood flow was measured in 29 adult female sheep using the radioactive microsphere technique. Basal blood flow, response to change in arterial carbon dioxide tension, and response to change in mean arterial blood pressure were determined. The results were compared to cerebral cortical blood flow values in the same sheep. Mean choroid plexus blood flow was 601 ml/100 g/min under basal conditions. Choroid plexus blood flow fell 31% with hypocarbia, a reduction comparable to that seen in cortex. With hypercarbia choroid plexus blood flow rose only 27% whereas cortical blood flow increased by 199%. Unlike cortical blood flow, choroid plexus blood flow fell significantly with pharmacogenic hypertension. The latter finding may reflect the absence of a blood-brain barrier in choroid plexus.