The transendothelial DC potential of rat blood-brain barrier vessels in situ

The recorded potential between the abluminal CSF and the vessel lumen, 3-4 mV, blood negative is similar to that recorded in frog and can account for most or all of the previously-reported PD between CSF and blood. It is not affected by substances that alter paracellular permeability and hence is mainly generated by the properties of endothelial cell membranes. Unlike the PD recorded in frog brain vessels, the PD in rat is not sensitive to the Na(+)-K+ATPase inhibitor, ouabain, which suggests that although electrogenic Na(+)-K+ transport is known to be present, the contribution it makes to the PD is not detectable. This suggests that the changes in PD recorded when abluminal [K+] or [Na+] are altered, are a result of the passive permeability properties of the endothelial cell membranes.