Vascular effects of acetazolamide on the choroid plexus.

Decreases in production of cerebrospinal fluid (CSF) after administration of acetazolamide have been attributed in part to constriction of blood vessels of the choroid plexus. The first goal of the present study was to examine effects of acetazolamide on blood flow to the choroid plexus. We measured blood flow (microspheres) and the production of CSF (ventriculo-cisternal perfusion) in anesthetized rabbits. Under control conditions, blood flow to the choroid plexus was 466 +/- 34 (mean +/- S.E.) ml min-1 100 g-1 and CSF production was 9.4 +/- 0.9 microliters min-1. Acetazolamide (25 mg kg-1 i.v.) decreased production of CSF by 55 +/- 5% despite a 2-fold increase in blood flow to the choroid plexus. The second goal of this study was to examine the role of hypercapnia, which occurs after administration of acetazolamide, in producing increases in blood flow. In animals in which hypercapnia was prevented by increases in ventilation, acetazolamide produced a similar increase in blood flow to the choroid plexus. We conclude that acetazolamide decreases the production of CSF but, in contrast to predictions based on studies in vitro, acetazolamide produces a marked increase in blood flow to the choroid plexus. Thus, changes in blood flow to the choroid plexus and production of CSF are uncoupled after administration of acetazolamide.