Figure 4. Environment enrichment reveals an LTP phenotype in ArcKR mice.
A, Graph plotting mean normalised (to the baseline) fEPSP slope against time for WT (n = 11 slices, 6 mice) and ArcKR mice (n = 11 slices, 5 mice) in standard housing. After a 20-minute baseline, LTP was induced with theta burst stimulation (TBS, 3 trains separated by 20s, with each train consisting of 10 bursts of 4 pulses at 100 Hz, separated by 200 ms). Inset, example fEPSP waveforms before and after LTP induction (average of waveforms at 55-60 minutes) from WT and ArcKR mice. B, Bar chart plotting the mean potentiation of fEPSP slope 55–60-minute post-LTP induction. There was no significant difference (P = 0.652, Z = 0.459, U = 68, Mann Whitney) in the amplitude of potentiation between WT (122.65 ± 24.6 %) and ArcKR slices (88.5 ± 13 %). C, Bar chart plotting the mean ratio of LTP (55-60-minute post induction) to STP (5 minutes post induction). There is no significant difference in the ratios (mean ratio: WT 0.95 ± 0.1; ArcKR 0.4 ± 0.03 P = 0.623, Z = -0.49, U = 63, Mann Whitney. D, Graph plotting mean fEPSP slope against stimulus strength for WT (n = 31 slices, 11 mice) and ArcKR mice (n = 43 slices, 14 mice) housed in environmentally enriched conditions. There was no significant difference (F(df)1, F=1.673, p=0.208 Two-way repeated measures ANOVA) between WT and ArcKR stimulus input/output relationships. Inset, superimposed fEPSP waveforms at increasing stimulus strengths (0.5 to 5 V) from a WT and ArcKR slice. E, Graph plotting mean paired-pulse ratio against paired pulse interval for WT (n = 18 slices, 7 mice) and ArcKR mice (n = 20 slices, 9 mice) housed in environmentally-enriched conditions. There was no significant difference (F(df)1, F=1.302, p=0.270 Two-way repeated measures ANOVA) in paired-pulse facilitation between WT and ArcKR mice. F, Graph plotting mean normalised (to the baseline) fEPSP slope against time for WT (n = 10 slices, 9 mice) and ArcKR mice (n = 16 slices, 11 mice) housed in environmentally-enriched conditions. After a 20-minute baseline, LTP was induced with theta burst stimulation (TBS, 3 trains separated by 20s, with each train consisting of 10 bursts of 4 pulses at 100 Hz, separated by 200 ms). Inset, example fEPSP waveforms before and after LTP induction (average of waveforms at 55-60 minutes) from WT and ArcKR mice. B, Bar chart plotting the mean potentiation of fEPSP slope 55–60-minute post-LTP induction. There was no significant difference (mean LTP; WT 83.2 ± 16.3; ArcKR 54.2 ± 8.5 %, P = 0.265, Z = 1.11, U = 1.3, Mann Whitney) in the amplitude of potentiation. C, Bar chart plotting the mean ratio of LTP (55-60-minute post induction) to STP (5 minutes post induction). The ratio was significantly smaller in ArcKR mice (mean ratio: WT 0.88 ± 0.04; ArcKR 0.78 ± 0.03 P = 0.0123, Z = 2.5, U = 153, Mann Whitney. Data are represented as mean ± SEM. The data points in (B, C, G and H) show the mean data for individual experiments.