Cerebral vessels have the capacity to transport sodium and potassium.

The activity of Na+, K+-activated adenosinetriphosphatase and the uptake of a potassium analog, rubidium, were found to be similar in cerebral microvessels and choroid plexus when measured in vitro. This similarity suggests that sodium and potassium concentrations in the nascent brain extracellular fluid are determined by the same active process that regulates their concentration in nascent cerebrospinal fluid. The brain microvessels may thereby play on active role in brain potassium homeostasis and brain extracellular fluid formation.