Mechanism of delayed intracranial hypertension after cerebroventricular infusions in conscious rats

Dexamethasone and Ergonovine Effects on Cerebrospinal Fluid Pressure in Conscious Rats

“…However, between 2 and 4 h, an exponential rise oc curred that lasted for 24 h. Dividing these infusion volumes equally into both lateral ventricles yielded the same results except that the rise in CSFp was higher and some rats developed neurological signs by 24 h [10]. Later studies demonstrated a delayed rise in CSFp after just the 10-min ICV infusion [14], We determined that CSFp, resistance to CSF outflow (Ro) and intracranial compliance (C) had all returned to normal 20 min after such a 10-min ICV infusion [14]. Later, when CSFp was elevated, Ro increased and C decreased.…”

“…Later, when CSFp was elevated, Ro increased and C decreased. The increased CSFp and Ro were indepen dent because inhibition of CSF synthesis pre vented the delayed rise in CSFp, but not Ro [14].…”

“…Pressure/volume tests were performed in these rats 20 min and 4 h after the 1CV infusion. This was done with a second pump connected to a digital timer that delivered an ICV bolus of aCSF (10 j.il/0.5 s) [14]. Except for the automatically delivered pressure/volumc tests, the rats were undisturbed in their cages with food and water for the 6-hour experiment.…”

“…The pressure/ volume tests utilized the 1/s data matrix. The first 5 s was censored as a bolus distribution period [14], The CSFp decay over the next 60 s was subjected to linear regression. Intracranial compliance (C) was calculated as:…”

“…Rats received a brief ICV infusion of aCSF, 8 pl/min for 10 min, to clear choroid tissue away from the needle tip, which was kept patent by a continuous infu sion of aCSF, 0.5 pl/min, for 24 h. A typical pressure/volume curve occurred during the 10-min infusion [10,14], and pressure re turned to normal within 15 min. However, between 2 and 4 h, an exponential rise oc curred that lasted for 24 h. Dividing these infusion volumes equally into both lateral ventricles yielded the same results except that the rise in CSFp was higher and some rats developed neurological signs by 24 h [10].…”