Figure 4.

Experience-Induced Plasticity of Spiny PVIs

(A) Left, confocal image showing PVIs with different expression levels of PV protein as detected by immunofluorescence (red). Middle, when analyzed for the entire PVI population, PV expression levels were only slightly higher in EE than in control mice (each data point represents PV expression in one cell; n = 168 cells, 3 control and 4 EE mice). Right, however, when analyzed separately these changes in PV expression were significant in spiny but not in non-spiny PVIs (n = 82 cells in 3 control and 4 EE mice).

(B) EE exposure increased the proportion of spiny PVIs (n = 144 neurons, 6 control and 4 EE mice).

(C) Total spine densities of individual cells as well as spine densities in the inner ml were unchanged after EE, but spine densities in the middle and outer ml were increased (n = 92 cells, 6 control and 4 EE mice).

(D) PNN wrapping of PVI somata was strongly reduced after EE compared to control conditions (n = 83 cells in 3 control and 4 EE mice).

(E) Total input density (identified as appositions of PSD95- and VGLUT1-positive puncta) of PVIs declined after EE exposure (n = 71 cells in 3 control and 4 EE mice).

(F–H) Example traces (F), frequency (G), and amplitude (H) of mEPSCs (n = 8 and 9 cells in 3 control and 4 EE mice) in PVIs of control and EE mice.

(I–K) Example traces (I), frequency (J), and amplitude (K) of mIPSCs (n = 5 and 8 cells in 3 control and 4 EE mice) in PVIs of control and EE mice. Note the decrease in frequency but increase in amplitude of mEPSCs.

(L) Whereas spiny and non-spiny segments displayed similar input densities (appositions of PSD95- and VGLUT1-positive puncta) in control mice, EE mice showed reduced input densities on non-spiny segments (n = 52 segments in 3 control and 4 EE mice). Bars are means ± SEM.