Hysteresis in the relationship between cerebrospinal fluid absorption minus formation and cerebrospinal fluid pressure in the dog.

In this study the difference between cerebrospinal fluid (CSF) absorption and formation (A -- F) was measured as a function of CSF pressure in the living and dead dog. We determined this relationship between A -- F and CSF pressure during both increasing and decreasing CSF pressures. A hysteresis effect was identified in 78% of living animals, but was not seen in the dead animals. This suggests that the mechanism of CSF absorption in the living dog is nonpassive and pressure-sensitive.