Quantitative autoradiography of binding sites for [3H]AMPA, a structural analogue of glutamic acid.

Binding sites for the potent glutamate agonist [3H] alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) were localized in rat brain frozen sections by quantitative autoradiography. Highest levels of binding were seen in stratum radiatum and stratum oriens of the CA1 hippocampal subfield and in the dorsal subiculum. Substantially less but still high amounts of [3H]AMPA binding occurred in other hippocampal subfields and in rostral forebrain structures. The heterogeneous nature of [3H]AMPA binding is discussed in relation to [3H]glutamate binding visualized by similar methods. From these data it is suggested that [3H]AMPA may label a particular subclass of the glutamate receptor population which exhibits a high affinity for quisqualic acid.