Using a patch-clamp, reverse transcription-polymerase chain reaction (RT-PCR) method, we determined AMPA receptor subunits expressed in neurons in rat hippocampal slices at the single-cell level. In a population of non-pyramidal neurons (type II neurons) expressing AMPA receptors with strong inward rectification and Ca2+ permeability, no GluR2 was detected, and GlIuR1 and GluR4 were the most frequently detected subunits. Analysis of the splicing variants revealed that only the flop form of GluR4 was expressed, but both flip and flop forms of GluR1 were expressed in these neurons. In contrast, GluR2 was the most frequently detected subunit both in CAI pyramidal cells and type I non-pyramidal cells possessing AMPA receptors with outwardly rectifying current-voltage relationships and little Ca2+ permeability: NeuroReport 11:3583-3587 (C) 2000 Lippincott Williams & Wilkins.