Fig. 1

Glutamate metabolism cycle: After release of glutamate from the presynaptic neurons, a small percentage of glutamate is taken up by post-synaptic glutamate receptors and transporters. While the majority of this synaptically-released glutamate diffuses out of the synaptic cleft is taken up by astrocytic EAATs and mGluRs. In astrocytes, glutamate could be converted to glutamine by glutamine synthetase (GS), then glutamine is released to the synaptic cleft to be taken up by presynaptic neurons and used to resynthesize glutamate. The synaptic vesicles (SVs) uptake the resynthesize glutamate by VGLUTs to release back to the synaptic cleft through synaptic vesicles cycle