Ectopic expression of inhibitory neuropeptide Y in the dentate gyrus of Tg2576 mice with aging.

<p>(A) Neuropeptide Y (NPY) immunoreactivity in the dentate gyrus of 18 months-old NTg and Tg2576 mice. Albeit NPY staining was observed in the soma of some hilar cells in both NTg and Tg2576 mice (enlargements), a massive ectopic NPY expression in the mossy fibers running from the hilus to CA3 (arrow) was evidenced in Tg2576 mice only. (B) NPY immunoreactivity (NPY-IR) was quantified in the molecular layer of NTg and Tg2576 mice as a function of age (in months) (n=5-10 mice/group). NPY expression remained stable through aging in NTg mice while it increased significantly in Tg2576 mice at 18 months compared to 3, 5 and 12 month-old Tg2576 mice and compared to age-matched NTg control mice. (C) Quantification of NPY expression in the mossy fibers of Tg2576 and NTg mice along aging. An ectopic expression of NPY was observed in the mossy fibers of several Tg2576 mice, in proportions that increased with age, becoming statistically significant at 18 months, as shown in the scattered plot where each dot represents a mouse. Quantitative data represent mean ± SEM in B and C. Data were analyzed by two-way ANOVA with Bonferroni post-hoc: ###p<0.001 age effect for each genotype; **p<0.01 Tg2576 mice <i>vs</i> age-matched NTg, two-way ANOVA. ML: molecular layer, GCL: granular layer, MF: mossy fibers, CA3: Ammon’s horn 3. Scale bar: A=300µm.