AMPA GLUTAMATE RECEPTORS AND THEIR FLIP AND FLOP MESSENGER-RNAS IN HUMAN HIPPOCAMPUS

AMPA-preferring glutamate receptor genes gluR1-4 undergo alternative s plicing into flip and flop mRNA isoforms. In the rodent hippocampus, g luR1 and gluR2 isoforms are differentially expressed. We have studied their distribution in human hippocampus. As in the rat, flop isoforms predominate over flip in dentate gyrus, whereas gluR1 flip is prominen t only in CA3. In contrast to the rat, flop mRNAs are clearly present in CA3. At a cellular level, pyramidal neurones express moderate amoun ts of each isoform. In several hippocampal fields, scattered non-pyram idal cells-putatively interneurones and glia-show abundant expression. The findings are supported by immunocytochemical detection of gluR1 a nd gluR2/3. As the four encoded isoforms have distinct properties, the ir differential expression within the hippocampus, and between species , should be taken into account when considering the roles of AMPA rece ptors in normal and abnormal brain states.