Expression of AMPA-glutamate receptor B subunit in rat hippocampal GABAergic neurons

The physiological properties of a-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type glutamate receptor (GIuR) channels are determined by their subunit composition. In particular, the expression of the GIuRB subunit determines the divalent ion selectivity of the channel. We studied the distribution of GIuR-B mRNA and protein in adult rat hippocampal GABAergic neurons combining non-radioactive in sifu hybridization with immunocytochemistry. The majority of GABAergic hippocampal neurons were GIuR-B mRNA-positive, but overall the levels of GIuR-B transcript were lower than in pyramidal and granule cells, which showed the highest hybridization signal. The different GIuR-B mRNA expression levels in GABAergic versus principal neurons were also observed at the protein level. There was a paucity of GIuR-B/C immunoreactivity in the vast majority of somata of the GABAergic neurons studied, which contrasted with the strong expression of GIuR-B/C proteins in the hippocampal principal neurons. Our results demonstrate the general low expression of the GIuR-B subunit mRNA and GIuR-B/C proteins in GABAergic hippocampal neurons. Considering the dominant role of the GIuR-B subunit in determining the divalent ion permeability of the receptor, it is likel