Fig. 3

PLX5622 treatment ameliorates ⁴He irradiation-induced, hippocampal-dependent, fear extinction memory impairments. a During the conditioning phase, all mice showed elevated freezing following a series of three tone-shock parings (80 dB, 0.6 mA, T₁–T₃). 24 h after the conditioning phase, fear extinction training was administered every 24 h (20 tones) for 3 days in the same environment (spatial and odor context). All mice showed a gradual decrease in the freezing behavior (day 1–3) except ⁴He-irradiated mice (30 cGy + Con chow) which showed a significantly higher time in freezing compared to other groups (0 Gy + Con chow, 0 Gy + PLX5622 and 30 cGy + PLX5622; *p < 0.01; **p < 0.001). b During the extinction test (24 h after extinction training), control mice receiving vehicle or drug treatment (0 Gy + Con chow and 0 Gy + PLX5622) showed abolished fear memory compared to ⁴He exposed mice given vehicle (30 cGy + Con chow, *p < 0.01). In contrast, the freezing levels for the ⁴He-irradiated mice receiving PLX5622 were comparable to the control mice (0 Gy + Con chow). c Comparison of percentage time freezing during the first day of extinction training phase versus extinction test day show significant differences for each experimental cohort. Data are presented as mean ± SEM (n = 8 per group, a). p values are derived from repeated-measures two-way ANOVA and Bonferroni’s multiple comparisons test. *p < 0.05 and **p < 0.01 compared with the 30 cGy + Con chow group (a, b); ***p < 0.0001 compared with percentage freezing (first five tones) during the extinction training day 1 (c)