Glutamate Uptake by the Isolated Toad Brain

Abstract
The isolated toad brain accumulates L-glutamate against strong concentration gradients until a tissue-to-medium concentration ratio of about 3000 : 1 is attained. The accumulated glutamate does not equilibrate with most of the endogenous tissue glutamate but is converted rapidly to glutamine and released into the medium. This mechanism may be involved in the preservation of low extracellular levels of cerebral glutamate.