Figure 5.

Disynaptic GABAergic transmission in the CA1 involves activation of interneurons with CP-AMPARs. CP-AMPAR blocker PhTx (10 μm) strongly inhibits disynaptic IPSCs recorded in the pyramidal cell soma. The effect of PhTx was studied at three different IPSC amplitudes relative to the maximum (maximum, 75%, and 30% amplitudes) and was most pronounced at lower amplitudes of disynaptic IPSCs, indicating strong contribution of interneurons with CP-AMPARs. A, Top, IPSC averages in one experiment. Symbols indicate ctrl, +PhTx, and +NBQX as below. Bottom, Histogram shows IPSC amplitudes at three different stimulus intensities relative to the maximum disynaptic IPSC. IPSCs were evoked by extracellular stimulation in oriens/alveus close to subiculum. Schematic shows experimental design. Open bars show IPSCs (mean ± SE) in control, and gray bars show IPSCs after wash-in of PhTx (15 min) (*p < 0.05, **p < 0.01, ***p < 0.005, paired t test). Disynaptic origin of IPSCs was confirmed at the end by NBQX application (10 μm, filled bars). WhC, Whole-cell mode. B, Temporal properties of blocking disynaptic IPSCs by PhTx when 30% of maximum IPSC was used throughout experiment. Horizontal bars indicate timing of drug application as indicated. Top, Consecutive IPSCs in one experiment during baseline and after exposure to the drugs.