Immunocytochemical study by two photon fluorescence microscopy of the distribution of GABA_A receptor subunits in rat cerebellar granule cells in culture

Summary.

An immunocytochemical investigation of the expression of α₁, α₆, β_2/3, γ₂ and δ subunits was performed on rat cerebellum granule cells in culture by the two photon microscopy technique.

The first four subunits appear to be expressed abundantly in these cells, whereas the δ one seems to be expressed at a lower level. Another major difference in the distribution of these subunits is that whereas α₆, β_2/3 and γ₂ appear only on plasma membranes α₁ and δ are present mainly in the cell bodies cytoplasm. Still another difference was found in that the presence of γ₂ on neurites is “polarized”, preferentially labelling neurites with the appearance of dendrites. The subunits α₆ and β_2/3 appear to label all types of neurites, with β_2/3 being by far the most heavily expressed subunit type. A final distinct characteristic is that α₆ and, even more, γ₂ appear to accumulate in the cytoplasmic domains immediately below the cone of emergence of neurites. This suggests a conspicuous transport of such subunits from the site of synthesis in the cell body to the site of final expression in the neurites (dendrites and axon terminals).