CSF pressure in fetal micein utero: External factors pressurize the intraventricular space

Abstract

AbstractPrevious experiments inducing leakage of embryonic cerebrospinal fluid (CSF) suggest the necessity of intraventricular CSF pressure (PCSF) for brain morphogenesis. Nevertheless, how embryonic PCSFoccurs is unclear, especiallyin utero. Using a Landis water manometer, we measured PCSFin fetal mice isolated from the amniotic cavity (PCSF-ISO). At embryonic day (E) 13, PCSF-ISOwas 82.7 Pa. Intraventricular injections of ≥2 μl of saline elevated PCSF-ISOby ∼30%. Intraventricularly injecting inhibitors of CSF secretion decreased PCSF-ISOby ∼30%. Shh-mediated cerebral-wall expansion and the resulting ventricular narrowing did not significantly increase PCSF-ISO. Removal of the brain-surrounding contractile tissues decreased PCSF-ISOby 80-90%. The intraamniotic pressure measuredin utero(PAF-IU) was 1030.7 Pa. Our direct measurement revealed that the PCSFin utero(PCSF-IU) was 1076.4 Pa, confirming the susceptibility of PCSFto external factors. Subsequent PCSFmeasurements under hydrostatic pressure loading suggested that PCSF-IU= PCSF-ISO+ PAF-IU, a relationship further used to estimate PCSF-IUat other ages when direct measurement was not possible. The estimated PCSF-IUdecreased almost constantly from E10 to E16 (2000 ➔ 500 Pa).