The first indication of 'metabolic compartmentation'in brain was the demonstration that
glutamine after intracisternal [14C] glutamate administration is formed from a compartment of
the glutamate pool that comprises at most one-fifth of the total glutamate content in the brain.
This pool, which was designated 'the small compartment,'is now known to be made up
predominantly or exclusively of astrocytes, which accumulate glutamate avidly and express
glutamine synthetase activity, whereas this enzyme is absent from neurons, which …