Fig. 4. Aged SynI^–/– and SynII^–/– mice have an increased neuronal loss in the CA1 region of the hippocampus. (A) Schematic drawing of a coronal section of mouse brain at bregma level –1.55 mm (modifed from the Allen Reference Atlas, http://www.brain-map.org/welcome.do). The boxed area corresponds to the region of the hippocampal field CA1 that was sampled in young (C) and aged (B,C) WT, SynI^–/– and SynII^–/– mice (11-12 mice per group). (B) Immunostaining with anti-NeuN antibody of 10-µm cryostat sections of the CA1 region of aged WT, SynI^–/– and SynII^–/– brains. Scale bar: 10 µm. (C) The counts of NeuN-stained nuclei in the sampled area of young and aged mice, plotted as mean percent changes ± s.e.m. with respect to age-matched WT mice, show a loss of pyramidal neurons in the CA1 hippocampal field of aged mutant mice. The counts of NeuN-stained nuclei/sampled area in WT mice were 97.0±2.9 and 102.9±2.0 for young and aged mice, respectively. Statistical analysis was performed by means of one-way ANOVA [F(2,32)=10.97, P<0.001] followed by Bonferroni's multiple comparison test (^*P<0.05, ^***P<0.001 vs WT).