FIG. 1.

Infection of hippocampal slices. (Top) Schematic representation of a hippocampal slice with the locations of CA1 and CA3 pyramidal cells and of a granule cell in the dentate gyrus (DG). The position of a glass micropipette, which contains the viral solution, inserted into the pyramidal cell layer (as indicated by the gray area) of the CA3 region is indicated. Arrows along the axons indicate the unidirectional progression of excitatory pathways, with mossy fibers from granule cells synapsing onto dendrites from CA3 pyramidal cells and Schaffer collaterals from CA3 pyramidal cells connecting to dendrites from CA1 pyramidal cells. Note that granule cells are presynaptic to CA3 pyramidal cells, which themselves are presynaptic to CA1 pyramidal cells, whereas this is normally not the case for the reverse. (Bottom) Photograph of a rat hippocampal slice cultured on a 12- by 24-mm glass coverslip.