HFS CA1 LTP is normal in Arc KO animals. A, There was no significant difference in basal synaptic transmission between Arc^GFP/GFP KO (red circles) and WT (black circles) littermates. B, There was no significant difference in the average magnitude of LTP over the first 5 min poststimulation, nor over the last 5 min of recording, between Arc^GFP/GFP, KO, and WT littermates when LTP was induced using a 2 × HFS (100 pulses at 100 Hz) protocol. C, There was no significant difference in the magnitude of LTP over the first 5 min poststimulation, nor over the last 5 min of recording (b), between the Arc^GFP/GFP, KO, and WT littermates when LTP was induced using a moderate frequency protocol (900 pulses at 10 Hz). D, There was no significant difference in the magnitude of E-LTP over the first 5 min poststimulation, nor over the last 5 min of recording, between the Arc^GFP/GFP, KO, and WT littermates when E-LTP was induced using weak, high-frequency stimulation protocol (20 pulses at 100 Hz). Data are represented as mean ± SEM. Scale bars: 0.5 mV (horizontal) and 5 ms (vertical).