Figure 1.

Glutamate (Glu) uptake and Glu/glutamine (Gln) cycle. Glu released from the nerve terminal by exocytosis is taken up by neuronal Glu transporter present presynaptically (1) and postsynaptically (2) and by glial Glu transporter (3). Glu/Gln cycle is one type of Glu recycling, but the significance is still unclear in vivo (see references 37 and 38). Astroglia detoxifies Glu by converting it to Gln. Glu is subsequently released from the glial cells by glial Gln transporter (4) and taken up by neuronal Gln transporter (5). Neurons convert Gln back to Glu, which is loaded into synaptic vesicles by vesicular Glu transporter (6). 7: postsynaptic Glu receptors.