Experiment 2: VV was measured at 5 day intervals during continuous intraventricular infusion of 10kD dextran yielding CSF osmolarities of 307 (isoosmolar) or 337 mOsm/L (hyperosmolar). Results are expressed as a percentage relative to normalized VVs measured prior to initiating ventricular infusion. VV in Group I (On-On-On 307 mOsm/L) increased incrementally at each time-point over the course of continuous iso-osmotic dextran infusion. VV in Group II (On-On-On 337 mOsm/L) also increased at each time-point over the course of continuous hyper-osmotic dextran infusion; however, these increases were larger and highly significant. VV in Group III (On-Off-On 337 mOsm/L), trended toward increase during interval A, slowed during interval B when infusion was suspended, and resumed increasing and reached significance during interval C when infusion was restored. VV in Group IV (On-Off-Off 337 mOsm/L), trended toward increase during interval A. The rate of increase slowed during intervals B and C when infusion was suspended but the increase in VV reached significance at both time-points.