DNA methylation regulates the extinction of fear memory

Figure 4 L-methionine promote the fear memory extinction. A: The DNA methylation level in hippocampus was significantly decreased after 7 days L-methionine (L-M)/vehicle injection (Unpaired t-test, T₈ = 3.409, P < 0.01); B: Experimental procedures. Vehicle group (7 days vehicle injection), n = 9; L-M group (7 days L-M injection), n= 10; C: F. cond, freezing levels of the last conditioned stimulus and unconditional stimulus (CS-US) pairing; Rec B, averaged freezing levels during four CS during recall. Significantly higher freezing levels in F. cond than those during recall in contexts B (two-way RM ANOVA, F. cond vs Rec B, vehicle, T₁₇ = 4.935, P = 0.0001; L-M, T₁₇ = 7.266, P < 0.0001); D-F: Freezing levels during the entire experimental course; E: Ext, significantly decreased freezing level in extinction procedure in the L-M group [two-way RM ANOVA, F_(1,17) = 5.353, P < 0.05]. No significant difference was found regarding fear conditioning Day 1 (E) and recall in Context B on Day 10 (F); G: Experimental procedures. Vehicle group, n = 12; L-M, n = 12; H: F. cond, freezing levels of the last CS-US pairing; Rec B, averaged freezing levels during four CS during recall. Significantly higher freezing levels in F. cond than those during recall in contexts B (two-way RM ANOVA, F. cond vs Rec B, vehicle, T₂₂ = 7.433, P < 0.0001; L-M, T₂₂ = 8.909, P < 0.0001); I-K: Freezing levels during the entire experimental course; E: Ext, significantly decreased freezing level in the first day of extinction procedure in L-M group [two-way RM ANOVA, F_(1,22) = 8.798, P < 0.01]. No significant difference was found on fear conditioning Day 1 (I) and recall in Context B on Day 10 (K). P < 0.05. ^aP < 0.05; ^bP < 0.01; ^cP< 0.001; ^dP< 0.0001.