Figure 5

Exposure to X-rays at E10, E11 or E12 compromises MWM learning in a timing-specific manner. Results of the Morris water maze (MWM) acquisition trials and the probe trial, performed at 4 days after the final acquisition trial block, are shown for 12-week-old male mice, irradiated at E10 (A, B), E11 (C, D) or E12 (E, F) with different doses of X-rays (0.0, 0.2, 0.5 or 1.0 Gy). (A, C, E) Escape latency during the MWM indicated that all mice improved their performance during the acquisition trial blocks, with no significant changes between sham-exposed animals and animals irradiated at E10 (A) or E12 (E). Contrarily, mice exposed to 1.0 Gy at E11 (C) showed a consistently higher escape latency when compared to controls or animals irradiated with lower doses at the same age. (B, D, F) Probe trial results further revealed an inferior memory ability in the animals irradiated at E10 and E11, shown by a similar amount of time spent in the opposite quadrant as in the target quadrant at 0.2 and 1.0 Gy (B) or a significant difference in time spent in the target quadrant at 1.0 Gy when compared to controls (blue asterisks in (D)). Animals exposed to radiation at E12 (F) did not differ in target preference. Orange asterisks in (B, D, F) indicate significant differences in time spent in the adjacent Q1 quadrant as opposed to the target quadrant for each experimental group. Similarly, green and red asterisks point out significant differences in time spent in the adjacent Q2 and opposite quadrant, respectively. Data are presented as mean + SEM. *P < 0.05, **P < 0.01, ***P < 0.001. The number of animals used is indicated in the acquisition graphs (N).