Figure 1. Expression of a degradation-resistant form of Arc (Arc(K268A;K269A); ArcKR), does not affect basal synaptic transmission or basal Arc protein expression levels but significantly enhances PP-LFS-induced long-term depression.
A, Graph plotting mean fEPSP slope against stimulus strength for WT (n =17 slices, 10 mice) and ArcKR mice (n = 17 slices, 9 mice). Inset, superimposed fEPSP waveforms at increasing stimulus strengths (0.5 to 5 V) from a WT and ArcKR slice. B, Graph plotting mean paired-pulse ratio against paired-pulse interval for WT (n =13 slices, 6 mice) and ArcKR mice (n =15 slices, 6 mice). C, Bar graph showing no difference between Arc protein levels in hippocampal lysate obtained from WT (n = 4) and ArcKR (n = 4) mice (p = 0.944). GAPDH was used as loading control. Inset, example western blots for Arc and GAPDH. Statistical comparisons were performed with one-way analysis of variance (ANOVA) followed by Tukey’s multiple comparisons. D, Graph plotting mean normalised (to the baseline) fEPSP slope against time. Long-term depression was induced with low frequency paired-pulse stimulation (LFS-PP; 900 paired-pulse at 1 Hz, interval between pulses 50 ms). Inset, example waveforms from WT and ArcKR mice. E, Bar chart summarising mean percentage depression 55-60 minutes after LFS-PP stimulation (WT n =10 slices 4 mice; ArcKR n = 11 slices, 6 mice). The amplitude of depression was significantly (p = 0.0358, U = 28, Z = -2.07 Mann Whitney) enhanced in slices from ArcKR mice (mean depression in WT 21.1 ± 4.3 compared to 35.8 ± 4.3 % in ArcKR mice). Data are represented as mean ± SEM. Data points are from individual experiments.