Figure 1.
Laminar distribution and structural differences of WFA-positive PNNs in V1, mEC, and hippocampus. A, Sagittal section of a rat brain stained with Neurotrace (Nissl bodies) and WFA. Brain areas are indicated based on the Paxinos atlas of the rat brain, with the areas of interest denoted. Lower panel shows the areas of interest highlighted, mEC in a sagittal plane, while V1 and hippocampus are shown in coronal plane. B, Expression of PNNs was quantified by intensity measurement and counting the fraction of PNN-enwrapped cells. The intensity measurements showed that expression was highest in V1 and CA2. WFA intensity from all areas was normalized to the values from V1. The fraction of neurons enwrapped by PNNs were quantified by manual counting and showed a layer-specific expression of PNNs. While the area averages (8.4% for V1, 7.9% for mEC) of PNN-positive neurons were similar between the areas, the layer-specific expression was different. Measurements were performed in three sections from three rats, bar graphs shows mean ± SEM. C, In V1, PNNs are uniformly expressed across cell layers, with the highest expression in Layer IV and the lower part of Layer V (left). In mEC, PNNs are densely expressed in Layer II/III with only sparse labeling in Layer V and VI (middle). The dorsal hippocampus (right) is largely void of PNNs, with the exception of area CA2 and partially CA3, which shows dense labeling of diffuse PNN-like structures. Intensity measurements across cell layers in V1 and mEC was performed in three sections from three rats and is shown as mean ± SEM. D, The structure of WFA-positive PNNs is highly variable between brain areas. High-resolution images from the V1 (left) show PNNs enwrapping the soma and the most proximal dendritic segments; from the mEC (middle) where the PNNs enwrap the cell soma extending far out in the proximal dendrite, and from the CA2 (right) where the PNNs are diffuse in structure and only embody the cell soma and neuropil.