Figure 2.

Fear stress disrupts nesting behavior and impairs hippocampus-dependent memory in E2 mice. (a) Representative images of nest building and corresponding scores. (b) Nesting scores did not differ by APOE genotype when mice were given 48 h to construct a nest in their home cage under normal, unstressed conditions. (c) When given 48 h immediately following fear stress, E2/E2 mice constructed less complex nests. (d) Learning curves during the Visible and Hidden sessions of the water maze were similar between all groups. (e) Long-term spatial memory was measured 72 h after training session 8 (Memory Test 1). All mice, regardless of APOE genotype, showed a preference for the target quadrant during the unstressed probe trial, indicating robust memory. (f) Seventy-two hours after training for a new platform location, long-term spatial memory retention was measured immediately after mice were exposed to a fear stress. Representative heat maps demonstrate inaccurate search patterns during the poststress memory test in mice with E2. (g) Mice with E2 failed to show preference for the target quadrant following fear stress, suggesting impaired hippocampus-dependent, long-term memory following a traumatic experience; n=9–12 per group. Groups labeled with dissimilar letters are significantly different (p<0.05, analysis of variance (ANOVA) followed by t-test). (e and g) *P<0.05 for T vs R, L, O; **p<0.01 for T vs R, L, O; ^#p<0.05 for T vs R, O, p=0.08 T vs L).