Ion dynamics at the energy-deprived tripartite synapse
Fig 2
Glutamate recycling scheme, inspired by combining vesicle-based models from [42] and [43].
(Left) Closer view of the model scheme at the synapse and (Right) the glutamate recycling scheme. Inactive neuronal intracellular glutamate (I) moves to the depot (D) from where it is packed into vesicles which pass through five stages (N, R, R1,2,3) before they are released into the synaptic cleft (F). These stages have fast time-constants that depend on intracellular Ca2+ concentration. The stages Ri correspond to vesicles that are bound by i Ca2+ ions. The time-constants change when there is influx of Ca2+ in the presynaptic terminal in response to membrane depolarization. Released glutamate in the cleft can be taken up by astrocytes or back to neurons using excitatory amino acid transporters (EAATs) or leak channels, thereby recycling the released neurotransmitter.