Fig. 1. The glutamatergic synapse. Glutamate is packaged into presynaptic vesicles and released to the synaptic cleft where it acts upon ionotropic and metabotropic receptors and is rapidly cleared by EAATs. In the astrocyte, glutamate either enters the TCA cycle or is converted to glutamine by the enzyme glutamine synthetase. Glutamine is then released to the presynaptic neuron where it is converted to glutamate and packaged into vesicles for further release.
