Figure 6

Cage activity and motor behaviour are affected time-dependently by irradiation at the onset of neurogenesis. Results of the 23-h horizontal cage activity task (A, B, C) and of the accelerating rotarod test (D, E, F), both performed in 12-week-old male mice, irradiated at E10 (A, D), E11 (B, E) or E12 (C, F) with different doses of X-rays (0.0, 0.2, 0.5 or 1.0 Gy). (A, B, C) Recordings for each 30-min time interval revealed an unchanged circadian cage activity profile in animals irradiated at E10 (A). Mice exposed to 0.5 Gy at E11 (B) showed a mild hyperactivity during the dark phase of the circadian cycle. In animals exposed to radiation at E12 (C), a nocturnal hyperactivity was also observed, already from a dose of 0.2 Gy onwards, and was accompanied by a decreased horizontal activity during the light phase, i.e. between 16 and 20 h. Orange asterisks represent significant differences in mice irradiated with 0.2 Gy, green asterisks in mice irradiated with 0.5 Gy and red asterisks in mice irradiated with 1.0 Gy, all compared to non-irradiated controls. (D, E, F) Performance on the accelerating rotarod apparatus was strongly affected in the group of 1.0-Gy-irradiated mice at E11 (E) during each of the four trials as compared to all other conditions (indicated as reduced latency values). Animals exposed to radiation at E10 (D) or E12 (F) did not display a changed latency in the accelerating rotarod. Data are presented as mean + SEM. *P < 0.05, **P < 0.01, ***P < 0.001 for comparison with controls. The number of animals used per test is indicated in the graphs (N).