The cerebrospinal fluid (CSF) has presented physiologists with an enigma for centuries. Reference to CSF in medical texts endows it with such functions as flotation of the brain, shock absorption, temperature regulation and waste disposal. However, all but flotation could arguably be ascribed to the immense vascular supply and capillary bed contained within the parenchyma of the brain. Significantly perhaps, the entire central nervous system begins as a fluid-filled neural tube and the fluid system is retained through development until, in some vertebrates, including humans, the tube is sealed in the spinal cord. CSF remains in the adult brain and is secreted by the choroid plexuses throughout life at a rate that produces four times the volume held in the fluid compartments per day. What then is the significance of this fluid?

Recent interest in CSF highlights the potential role of this fluid as a signal pathway (Nicholson, 1999; Johanson & Jones, 2001). Intense interest in brain development, and in particular development of the cerebral cortex, has exposed another potential role for CSF, a role co-ordinating the activity of germinal cells lining the cerebral ventricles and Cajal-Retzius cells in the marginal zone (Marin-Padilla, 1998; Super et al. 1998; Meyer et al. 2000). In fetal-onset hydrocephalus there is retardation in the development of the cortex coincident with an obstruction of CSF flow. Cells of the germinal epithelium fail to proliferate and produce the number of neurones generated in normal cortex (Mashayekhi et al. 2001). However, neuronal progenitors from the hydrocephalic cortex proliferate as normal in vitro and CSF collected from lateral ventricles of the hydrocephalic cortex inhibits in vitro proliferation of neuronal progenitors (Draper et al. 2001). Analysis of normal and hydrocephalic CSF reveals protein differences that could underlie these effects.

This work was carried out by the Neuroscience Group with funding from The Wellcome Trust.