Kaolin-induced hydrocephalus impairs CSF secretion by the choroid plexus.

CSF volume flow and sodium (Na+)-influx rates in normal and kaolin-induced hydrocephalic cats were measured during ventricular perfusion with anisotonic sucrose solutions. When ventricular fluid osmolality was 120 mOsm, CSF volume flow ceased for both groups of cats. As ventricular fluid osmolality was increased, the CSF volume flow rate of normal cats increased to 70 microliter per minute, and in hydrocephalic cats to 40 microliter per minute. In normal cats, for ventricular fluid osmolality between 50 and 350 mOsm, Na+-influx was constant and thought to occur by diffusion; while for higher osmolalities, Na+-influx increased. In hydrocephalic cats, Na+-influx increased over the entire range of ventricular osmolality but was less than in normal cats. Acetazolamide decreased the CSF volume flow in normal cats by 40 percent, but was ineffective in hydrocephalic cats. These results suggest that CSF secretion by the choroid plexus of cats with kaolin-induced hydrocephalus is impaired.