The effect of cerebrospinal fluid pressure on dural venous pressure in young rats

In order to study cerebrospinal fluid (CSF) absorption across the dural sinus wall, the effect of CSF pressure (recorded from the cisterna magna) on dural venous pressure (recorded from the transverse sinus) was investigated in groups of rats at 2, 10, 20, and 31 days after birth and in adulthood. At normal resting pressures there was no positive pressure gradient between the CSF and sinus venous blood in 2-, 10-, and 20-day-old rats, but in 31-day-old and adult rats there was a positive gradient of 16 and 12 mm H2O, respectively. A series of constant-rate infusions of artificial CSF was made into the cisterna magna, and subsequent plateaus in both CSF and venous blood were recorded. The gradient of a plot of plateau pressure against infusion rate gave the overall resistance to absorption of the CSF for each age group, which was higher in 2- and 10-day-old rats than at three older ages. The effect on dural venous pressure was age-related, with the largest increase at 2 days, the smallest at 20 days, and no effect at 31 days or in adults. The pressure difference between CSF and sinus blood has been used to calculate resistance to absorption across the sinus wall. This showed that the high overall resistance to drainage in young rats can be largely accounted for by the rise in sinus pressure. It is concluded that drainage of CSF into the sinuses is greatly restricted in young animals.