Figure 1.

Glutamatergic synaptic transduction and uptake and metabolism of glutamate in the Müller cell. The photoreceptor cell synthesizes glutamate, which is continuously released during darkness. Glutamate released from the synaptic terminal reaches to the postsynaptic receptors of bipolar cell dendrites, then is promptly taken up from the synaptic cleft. The glutamate transporters are the predominant mechanism for uptake of glutamate in the Müller cell, and maintain the proper concentration of this potentially excitotoxic amino acid. Glutamate transported into the Müller cell is degraded to glutamine by glutamine synthetase.