LOCALIZATION OF THE GLUTAMATE-RECEPTOR SUBUNIT GLUR1 ON THE SURFACE OF LIVING AND WITHIN CULTURED HIPPOCAMPAL-NEURONS

The distribution of the glutamate receptor subunit GluR1 was investiga ted in cultured hippocampal neurons by confocal microscopy, using poly clonal antibodies directed against either the Nor C-terminal region. O n living neurons, GluR1 immunofluorescence was detected with the N-ter minal antibody only. GluR1 was localized in a highly punctate manner o n the surface of neuronal soma and throughout the dendritic tree. Many GluR1 puncta co-localized with the synaptic marker synaptophysin, alt hough extrasynaptic GluR1 puncta were also observed. A comparison of G luR1 subunit distribution of living neurons labelled with N-terminal a ntibody with that obtained after the cells had been fixed, permeabiliz ed and subsequently reacted with C-terminal or additional N-terminal a ntibody showed a number of differences. In permeabilized cells additio nal, diffuse labelling was observed which was very pronounced in the s oma and extended into the proximal dendrites. Furthermore, some spines showed little or no labelling of their membrane surface, but labelled strongly after the cells had been fixed and permeabilized. Such spine s may be the postsynaptic components of silent or suboptimal synapses. Copyright (C) 1996 IBRO.