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.