Activation of mGluR I suppressed GABAergic eIPSCs in WT and produced variable effects in Fmr1 KO neurons. A, Application of 3,5-DHPG (200 μm) suppressed the GABAergic eIPSC in a WT neuron. B, In a Fmr1 KO neuron, the GABAergic eIPSC amplitude was not affected by 3,5-DHPG. Averaged eIPSCs from the paired pulse stimulus (bottom) show eIPSCs under control (black) and 3,5-DHPG (purple) conditions. C, Mean GABAergic eIPSC amplitude was significantly reduced by 3,5-DHPG in WT (n = 6) but not Fmr1 KO neurons (n = 8). D, Normalized GABAergic eIPSC amplitude for individual neurons show a consistent suppression of eIPSC amplitude in WT (n = 6), but in Fmr1 KO, the effect of 3,5-DHPG is highly variable (n = 8). Decay tau (E) and PPR (F) did not significantly differ between drug conditions or genotypes. *p < 0.05.