DNA methylation regulates the extinction of fear memory

Figure 1 N-phthalyl-L-tryptophan (RG108) inhibited the extinction of fear memory. A: The DNA methylation level in hippocampus was significantly decreased after 2 hours of RG108 injection (unpaired t-test, T₉ = 4.291, P < 0.01); B: Experimental procedures. Vehicle, n = 10; RG108, n = 12; C: Fear. cond, freezing levels of the last conditioned stimulus and unconditional stimulus 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 in vehicle group but not in RG108 group (two-way RM ANOVA with multiple comparisons, F. cond vs Rec B, vehicle, T₂₀ = 2.564, P < 0.05; RG108, T₂₀ = 0.2606, P = 0.7971) and vehicle group showed significant lower freezing level in Rec B compared with the RG108 group (T₄₀ = 2.683, P < 0.05); D-F: Freezing levels during the entire experimental course. Recall in Context B, significantly higher freezing level in RG108 group (two-way RM ANOVA, F_{(1, 20)} = 9.063, P < 0.01). ^aP < 0.05; ^bP < 0.01; ^cP< 0.001.