Fig. 6

GluA4 is the molecular substrate mediating the acceleration in gating kinetics of eEPSCs and mEPSCs. a Examples showing immunofluorescent double-labeling of presynaptic terminal with tracer Alexa 555 (Red) and GluA4 antibody (Green) in synapses with or without TBS treatment. The same TBS paradigm as in Fig. 1 was delivered directly through presynaptic current injections (0.5–1 nA, 0.2 ms) with pipettes containing Alexa555 labeled dextran to allow post hoc identification of stimulated synapses in fixed slices (n = 4 slices from 4 mice). Naïve synapses were only injected with Alexa 555 but devoid of TBS paradigm as control. Average GluA4 membrane staining intensity was measured for the entire postsynaptic cell (representative z-stack section with the GluA4 intensity measured between white hatched lines). Scale bars: 10 μm for all panels. b Overlay of raw (top panels) and averaged eEPSCs (bottom panels) from naive (left column) and TBS treated synapses (right column) from GluA4^−/− mice with the accompanying dual exponential curve fits to the averaged traces and time constants given. c-d Summary plots of averaged Ƭ_fast and Ƭ_slow values of eEPSCs as well as the amplitude from naive and TBS synapses. e Raw and scaled mEPSCs from naive and TBS treated GluA4^−/− synapses are shown. f-g Plots of averaged mEPSC amplitudes and frequency from naive and TBS treated GluA4^−/− synapses. h Individual Ƭ_fast values of mEPSCs from pooled naive GluA4^−/− and TBS GluA4^−/− populations plotted on a conventional histogram normalized for area under the curve, showing no change in the relative proportions of two cohorts of mEPSCs (μ_0.8 and μ_1.5). i Comparison of Ƭ_fast histograms of mEPSCs from WT naive and GluA4^−/− naive synapses reveals the μ_0.4 cohort in WT synapses is absent in GluA4^−/−synapses