ARC and fragile X syndrome: 5 min after DHPG stimulation, the expression of ARC protein increased significantly in FXS C1 (FXS C1 0 min: mean = 0.76 ± 0.05, FXS C1 5 min: mean = 1.10 ± 0.13, p = 0.042) but not in FXS C1-cKO (FXS C1-cKO 0 min: mean = 0.58 ± 0.09, FXS C1-cKO 5 min: mean = 0.60 ± 0.11, p = 0.937) where ARC expression persisted at a consistent level over time without noticeable fluctuations (Figure 5B).