The TKO hippocampal CA3 regions show altered mossy fiber projection and sprouting.

<p>Timm staining of the Zn²⁺-containing mossy fiber terminals was performed on the hippocampus of WT and TKO mice at ages of 8–10 months. (A and A-a) Mossy fibers in the WT brains were terminated in the stratum lucidum, above the CA3 pyramidal cells layer (arrowheads), and below and within the pyramidal cell layer in the proximal portion of CA3 (half-open arrowhead). (B and B-b) Mossy fiber sprouting in the suprapyramidal bundle (arrows), and a fuzzy distal boundary of the suprapyramidal bundle spreading across the pyramidal cell layer into CA2 (asterisk) were shown on the TKO brain sections. Triangle in (B) shows the lightly stained and diffused intra and infrapyramidal bundles. Scale bars, 100 µm in (A and B), and 50 µm in (A-a and B-b).