Figure 4.
Reduced retrograde transport of 125I-NGF from hippocampus to BFCNs in Ts65Dn mice. Comparison of the retrograde transport of 125I-NGF from the hippocampus to the septum via the fimbria in 2N (white) and Ts65Dn (black) mice at 6 months of age. Radiolabeled NGF was injected into the dorsal hippocampus. Following intervals of 1.5, 3, or 6 h, the hippocampus, fimbria, and septum were dissected, and the fimbria was subdivided as defined in Materials and Methods. In 2N mice, 125I-NGF moved progressively in a wave through the proximal (i.e., closest to the hippocampus, fimbria 3), intermediate (fimbria 2), and distal segments (i.e., closest to the septum, fimbria 1) of the fimbria, arriving in the septum 6 h after injection. In contrast, in Ts65Dn mice there was little or no significant retrograde transport of 125I-NGF above background levels. The results shown are those for individual mice of each genotype at each interval for sacrifice; the results at 6 h were confirmed in two additional mice of each genotype. Failure of retrograde transport was also found in 12-month-old Ts65Dn mice (data not shown).