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Cell surface proteins that bind glutamate and directly gate ion channels in cell membranes. AMPA receptors were originally discriminated from other glutamate receptors by their affinity for the agonist AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid). They are probably the most common mediators of fast excitatory synaptic transmission in the central nervous system. Several subtypes have been cloned, and for some types the traditional distinction from kainate receptors may not apply.