File:Lu Nicoll 2009 FIG3.jpg

Figure 3.

Excitatory Synaptic Transmission at CA1 Pyramidal Neurons Is Mediated Primarily by GluA1A2 Heteromers (A) (A1 and A2) The time course for changes in AMPAR EPSCs in hippocampal slice cultures from GRIA1fl/fl mice after transfection of Cre-IRES-GFP. For ΔGluA1, shown are the ratio of AMPAR-EPSCs (closed circles, 3–5 days, 1.02; 6 days, 0.75; 7–8 days, 0.43; 9–10 days, 0.37; 11–12 days, 0.28; 12–14 days, 0.23; >14 days, 0.21) and ratio of NMDAR-EPSCs (closed diamonds, 3–5 days, 0.98; 6 days, 1.15; 7–8 days, 1.11; 9–10 days, 1.11; 11–12 days, 1.16; 12–14 days, 0.92; >14 days, 1.09) from transfected cells to neighboring control cells, respectively. (A2) Bar graph shows the percentage of AMPAR EPSCs (21.2% ± 3.1%; n = 15; ∗p < 0.0001) and NMDAR EPSCs (104.8% ± 17.6%; n = 14; p = 0.53) to controls. (B) (B1–B4) Scatter plots (B1 and B2) and bar graphs (B3 and B4) show amplitudes of EPSCs for single pairs (open circles) and mean ± SEM (filled circles) for GRIA1fl/fl (B1, pooled data from acute slices [P19–P24] from animals injected at P0–P2 and from hippocampal slice cultures) and GRIA3fl/fl (B2, data from acute slices [P20-P25] from animals injected at P0–P2), respectively. (Inset in B1 and B2) Sample traces are as follows: black, control; green, Cre. (B3) EPSC amplitudes show a significant reduction in AMPAR EPSCs for the deletion of either subunit (ΔGluA1, Cnt, −77.7 ± 12.7 pA; Cre, −15.1 ± 2.4 pA; n = 31, ∗p < 0.0001; ΔGluA3, Cnt, −56.4 ± 6.0 pA; Cre, −47.2 ± 5.6 pA; n = 19; ∗p < 0.05). (B4) There was no change in the NMDAR EPSCs (GluA1, Cnt, 40.0 ± 9.4 pA; Cre, 33.6 ± 6.9 pA, n = 29; p = 0.31; ΔGluA3, Cnt, 40.4 ± 7.7 pA; Cre, 39.0 ± 7.8 pA, n = 19; p = 0.97). (C and D) Bar graphs show average RI (C) (Cnt, 0.99 ± 0.03, n = 30; ΔGluA1, 1.02 ± 0.08, n = 14; p = 0.63; ΔGluA3, 1.06 ± 0.04, n = 15; p = 0.15) and average paired-pulse ratio (PPR, [D]) (Cnt, n = 84; ΔGluA1, n = 40; ΔGluA3, n = 9; p > 0.05 for both conditions). Left were sample traces. (E) Sample traces of mEPSCs shown at a low gain and sweep speed (traces on left; scale bar, 10 pA, 500 ms) and averaged mEPSCs at a high gain and sweep speed (traces on right). Control trace (black) has been superimposed on the trace from a Cre cell. Scale bar, 5 pA, 10 ms. mEPSCs were recorded from acute hippocampal slices (P20–P27) from animals injected at P0–P2. (F) (F1) Bar graphs show mEPSC amplitude (Cnt, −10.5 ± 0.4 pA; ΔGluA1, −7.9 ± 0.5 pA; ∗p < 0.001; ΔGluA3, −10.7 ± 0.1 pA; p = 0.77), (F2) frequency (Cnt, 0.28 ± 0.03 Hz; ΔGluA1, 0.08 ± 0.01 Hz; p∗ < 0.001; ΔGluA3, 0.27 ± 0.05 Hz, p = 0.68), and (F3) decay (Cnt, 11.30 ± 0.49 ms; ΔGluA1, 7.73 ± 1.41 ms; ∗p < 0.01; ΔGluA3, 11.60 ± 1.20 ms; p = 0.81). n = 22, 10, and 20 for Cnt, ΔGluA1, and ΔGluA3, respectively.