RELATIVE ABUNDANCE OF SUBUNIT MESSENGER-RNAS DETERMINES GATING AND CA2+ PERMEABILITY OF AMPA RECEPTORS IN PRINCIPAL NEURONS AND INTERNEURONS IN RAT CNS

Recording of glutamate-activated currents in membrane patches was combined with RT-PCR-mediated AMPA receptor (AMPAR) subunit mRNA analysis in single identified cells of rat brain slices. Analysis of AMPARs; in principal neurons and interneurons of hippocampus and neocortex and in auditory relay neurons and Bergmann glial cells indicates that the GluR-B subunit tn its flip version determines formation of receptors with relatively slow gating, whereas the GluR-D subunit promotes assembly of more rapidly gated receptors. The relation between Ca2+ permeability of AMPAR channels and the relative GluR-B mRNA abundance is consistent with the dominance of this subunit in determining the Ca2+ permeability of native receptors. The results suggest that differential expression of GluR-B and GluR-D subunit genes, as well as splicing and editing of their mRNAs, account for the differences in gating and Ca2+ permeability of native AMPAR channels.