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Excitatory amino acid transporters (EAATs), also known as ''glutamate transporters'', belong to the family of neurotransmitter transporters. Glutamate is the principal excitatory neurotransmitter in the vertebrate brain. EAATs serve to terminate the excitatory signal by removal (uptake) of glutamate from the neuronal synaptic cleft into neuroglia and neurons. The EAATs are membrane-bound secondary transporters that superficially resemble ion channels. These transporters play the important role of regulating concentrations of glutamate in the extracellular space by transporting it along with other ions across cellular membranes. After glutamate is released as the result of an action potential, glutamate transporters quickly remove it from the extracellular space to keep its levels low, thereby terminating the synaptic transmission.〔 Without the activity of glutamate transporters, glutamate would build up and kill cells in a process called excitotoxicity, in which excessive amounts of glutamate acts as a toxin to neurons by triggering a number of biochemical cascades. The activity of glutamate transporters also allows glutamate to be recycled for repeated release. Glutamate transporters also transport aspartate and are present in virtually all peripheral tissues including bone, heart, liver, and testes. They exhibit stereoselectivity for L-glutamate but transport both L- and D-aspartate. ==Classes== There are two general classes of glutamate transporters, those that are dependent on an electrochemical gradient of sodium ions (the EAATs) and those that are not (VGLUTs and xCT). The cystine-glutamate antiporter (xCT) is localised to the plasma membrane of cells whilst vesicular glutamate transporters (VGLUTs) are found in the membrane of glutamate-containing synaptic vesicles. Na+-dependent EAATs are also dependent on transmembrane K+ and H+concentration gradients, and so are also known as 'sodium and potassium coupled glutamate transporters'. Na+-dependent transporters have also been called 'high-affinity glutamate transporters', though their glutamate affinity actually varies widely.〔 Mitochondria also possess mechanisms for taking up glutamate that are quite distinct from membrane glutamate transporters.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Excitatory amino acid transporter」の詳細全文を読む スポンサード リンク
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