Figure 6. Retrogradely labeled cells in the entorhinal cortex are excitatory neurons.

A) Confocal fluorescence images of the same horizontal section of the ventral entorhinal cortex of a mouse that received a co-injection of rAAV5 driving GFP expression (green) and fluorescently labeled CTB (red) that was stained with DAPI (blue) and immunohistochemically labeled against the neuronal marker NeuN (magenta). Examples of individual GFP and CTB-labeled neurons are marked with white arrowheads. The white square denotes the area shown in higher magnification. Scale bars: low magnification: 100 µm, high magnification: 50 µm. B) Quantification of CTB positive cells and GFP positive cells (bars: mean±SEM; CTB: n= 918 cells, 4 sections, one mouse; GFP: n=264 cells, 4 sections, one mouse) with the neuronal marker NeuN showing in both cases almost complete co-labeling. C) Confocal fluorescence images of the same horizontal section of the ventral entorhinal cortex of a transgenic mouse in which GAD2-expressing interneurons are labeled by tdTomato (red) that received an injection of rAAV5 driving GFP expression (green) that was stained with DAPI (blue). Individual interneurons are marked with white arrowheads. The white square denotes the area shown in higher magnification. Scale bars: low magnification: 100 µm and high magnification: 50 µm) D) Quantification of GAD2-expressing interneurons and rAAV5 transduced neurons showing disjunct populations (bars: mean±SEM; n=1033 cells, 4 sections, one mouse).