Eva Ørnbo: "Cerebrospinal fluid production - passive or active water movement?"

PhD student, MacAulay Lab

Abstract: Humans produce approximately half a liter of cerebrospinal fluid (CSF) each day. Yet, we lack a comprehensive understanding of how the fluid is produced. The CSF production has, in general, been assumed to take place by osmosis, in which water passively crosses the CSF-secreting tissue choroid plexus from the blood and moves into the fluid-filled ventricular cavity in response to an osmotic gradient. We, however, demonstrated that neither rats, pigs nor humans, contain an osmotic gradient from blood to CSF to drive CSF production. We, moreover, observed that CSF could be produced in absence and even against osmotic forces in anesthetized rats. We propose that the novel concept of active cotransport of water can explain the mechanism by which CSF can be produced independent on osmotic gradients. The Na+/K+/2Cl- cotransporter NKCC1, which contains the feature of co-transporting water along with its ions, contributed to approximately 50% of the CSF production in rats. Active water transport therefore appears to be the primary driving force in CSF production in rats. With the knowledge of which transport proteins contribute to CSF production, targeted medicine against such transporting proteins could potentially help patients with excessive brain water with the act of lowering the CSF production.