Differences in Ca2+ permeability of AMPA-type glutamate receptor channels in neocortical neurons caused by differential GluR-B subunit expression

Abstract Fast excitatory synaptic transmission in the CNS is mediated by AMPA-type glutamate receptor (GIuR) channels. Heterologous expression suggested that the Ca 2+ permeability of these receptors critically depends on the sub-unit composition. Using patch-clamp techniques in brain slices, we found that the Ca 2+ permeability of native AMPA-type GluRs was markedly higher in nonpyramidal (PCaPK ≈ 0.63) than in pyramidal (PCaGPK ≈ 0.05) neurons of rat neocortex. Analysis of mRNA in single cells indicated that the relative abundance of GIuR-B-specific mRNA was significantly lower in nonpyramidal (GluR-BGluR-non-B ≈ 0.3) than in pyramidal (solGluR-BGluRnon-B ≈ 3) cells. This suggests that differences in relative abundance of GIuR-B-specific mRNA generate functional diversity of AMPA-type GIuRs in neurons with respect to Ca 2+ permeability.