Semiquantitative visualization of glutamate transporter distribution around two different types of synapses

The three different glutamate transporters (EAAT1-3) are found in the hippocampus, while four types (EAAT1-4) are found in the cerebellum (for more information see: Lehre and Danbolt, 1998; Danbolt, 2001). The quantitatively and functionally predominant glutamate transporter subtype is EAAT2 (also called GLT) which was the one isolated based on functional reconstitution of transport activity (Danbolt et al., 1990). This transporter is present in brain tissue at high concentrations (Lehre and Danbolt, 1998). The highest concentrations are found in the hippocampus and neocortex. Almost all the protein is present in astroglial cells in the mature and normal brain and spinal cord, but a few percent is expressed in terminals. EAAT2 is expressed in neurons during development and in retinal neurons also in the adult.

EAAT1 (GLAST) is exclusively glial, also during development, and is the major glutamate transporter in the cerebellum and in the retina.

EAAT3 (EAAC) is expressed at far lower concentrations. It is present in neurons throughout the nervous system; their cell bodies and dendrites, but not in the axons and terminals.

EAAT4 is virtually only expressed in the cerebellar Purkinje cells, and EAAT5 is a retinal protein.

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