Figure 2.

Photomicrographs of adjacent coronal sections through the Macaca fascicularis monkey hippocampal formation. A: Nissl-stained section. The pyramidal cell layer of the hippocampus and subiculum is demarcated with a black outline. B: Immunohistochemically stained section for the identification of the calcium-binding protein calretinin. White arrowheads indicate the moderately stained mossy fibers (mf). The border of the proximal portion of CA3 and the polymorphic layer (pl) of the dentate gyrus is indicated with black arrows. Dense staining of the inner third of the molecular layer (ml) is indicated with black arrowheads. Note that calretinin-like immunoreactivity is denser in the polymorphic layer of the dentate gyrus and thus defines the boundary between CA3 and the dentate gyrus C: Immunohistochemically stained section for the identification of nonphosphorylated high-molecular-weight neurofilaments (SMI32 antibody). Note that there is dark staining of the CA3 and CA2 pyramidal layers but there is little or no staining in CA1. This provides a stark contrast with the subiculum that contains moderately stained pyramidal cell bodies and heavily stained dendritic processes. The difference between the lack of staining in CA1 and the heavy labeling of the subiculum allows the precise determination of the oblique border between these fields (arrows). gcl, granule cell layer. Scale bar = 1 mm.