In astrocytic glutamate-glutamine cycle, the excess glutamate released by the pre-synaptic neuron in the synaptic cleft is transported into the astrocyte by a family glutamate transporters called the excitatory amino acid transporters 1 and 2, EAAT1 and EAAT2. Astrocytes carrying these transporters exist in close apposition to the synapse to clear excess glutamate to prevent excessive activation of neurons and hence neuronal death. Glutamate in astrocytes is converted to glutamine by glutamine synthetase. Glutamine is then transported into the extracellular space by system N transporters. The glutamate in the extracellular space is available for neuronal uptake.