Figure 4. Blocking NRSF Function Transiently after ELA Rescues Spatial Memory.

(A) A schematic of the mechanism by which the NRSE-ODN blocks NRSF function. The sequence of the synthetic, protected oligodeoxynucleotides (ODNs) replicates the recognition site for NRSF (NRSE). The ODNs, flooding the cells, bind available NRSF, acting as decoys and preventing NRSF binding to NRSE on genomic DNA (see also Figure 5E).

(B) H3K9 dimethylation at NRSE sites of the Npas4 gene was increased in adult dorsal hippocampus following ELA. Transiently blocking NRSF binding to chromatin with the use of NRSE-ODNs prevented this long-term ELA-provoked histone modification (significant main effects of ELA, F_[1,20] = 6.61, p = 0.02, and of NRSE, F_[1,20] = 4.97, p = 0.04; post hoc, p < 0.05).

(C) Memory for the prior location of a previously seen object was severely impaired in ELA rats receiving a random ODN sequence (Scrambled [SCR]) but was rescued in those receiving an NRSE-sequence decoy ODN to a level similar to that in control (CTL+SCR) rats. Two-way ANOVA demonstrated a significant interaction of the early-life experience and the type of treatment (F_[1,26] = 16.44, p = 0.0004), and post hoc analyses identified a significant effect of the NRSF blockade intervention (p < 0.05).

(D) In an independent measure of spatial memory, ELA+SCR rats could not reliably discriminate between the novel arm and the familiar arm of the Y-maze, which they had explored 4 h earlier (see Y-maze schematic). However, NRSF blockade prevented this spatial memory deficit (significant ELA × NRSE interaction, F_[1,25] = 7.26, p = 0.01, post hoc, p < 0.05). Representative heatmaps of the time spent in each area of the Y-maze are shown for each group, with the most time spent indicated with dark red and scaled through the least time spent represented with dark blue.

(E) Object recognition memory, which is less hippocampus-dependent, was unaltered by ELA or NRSF manipulation. Data in bar graphs of (C)–(E) are shown as the discrimination index: (time investigating novel location or object – time investigating familiar location or object)/(sum of time investigating both novel and familiar locations or objects).

(F–H) In contrast with the rescue of the impaired spatial memory, locomotion (open field test) (F), anxiety-like behaviors (elevated-plus maze) (G) and depressive-like behaviors (Porsolt forced-swim test) (H) were not affected by either the ELA or the ODN-NRSE treatment. Data are presented as mean ± SEM. *p < 0.05.

See also Figure S3.