Figure 7.

Labeling of dorsal MCs with mCherry and ventral MCs with eYFP demonstrate the progressive changes in their axonal projections throughout the DG in a series of transverse sections through an elongated hippocampus at 600-µm intervals. A–H, At rostral levels (A–D), mCherry-labeled MCs are abundant in the dentate hilus (H), deep to the granule cell layer (G). At more caudal levels (E–H), eYFP-labeled MCs predominate, and there is little overlap of the two labels in this animal. The dense axonal projections from caudal MCs (arrows) are strong and predominate at rostral levels (A–D), but are weaker at the level of their labeled cell bodies (E–H). The axonal projections from rostral MCs are occluded at rostral levels (A–C) where the ipsilateral projections of these neurons are weak, but the projections expand into the molecular layer at more caudal levels (D–H), forming a wider diffuse band (arrowheads) at anterior ventral levels (D, E) and a narrower band (arrowheads) at more caudal levels (F, G). At ventral levels, the innervation from rostral and caudal MCs form non-overlapping laminar distributions in the molecular layer (D–H). Scale bars: 200 µm (A–H).