Figure 3. PV cells hemizygous for Pten establish fewer connections to local pyramidal neurons.

(a) Examples of action potentials elicited in PV cells and pyramidal neurons during paired whole-cell recording experiments. Scale bars are 80 ms and 20 mV. (b) Examples of presynaptic action potentials and postsynaptic responses in paired recordings. All horizontal scale bars are 20 msec. (c) Probability of connection (ordinate) from PV cells to pyramidal cells in WT and PV-Pten heterozygous mice (P=0.025, Fisher's exact test; n=31 pairs in each genotype), pyramidal cells to PV cells (n=31 pairs from 10 mice in each genotype) and PV cells to neighbouring PV cells (n=33 pairs from 8 mice in each genotype). (d) Plot of evoked firing rates of pyramidal neurons to varying amounts of current injection in control, PV-Pten heterozygous mice (WT=10 cells, 3 mice; HET=10 cells, 3 mice; P=0.003, Kruskal-Wallis one-way ANOVA, followed by individual rank sum tests. P=0.02 for comparisons at 150 pA. For all other comparisons, P>0.05). (e) Same plot as in d, but following bath application of APV, picrotoxin and CNQX (WT=15 cells, 3 mice; HET=12 cells, 3 mice; P=0.92, Kruskal-Wallis one-way ANOVA). (f) Plot of amplitude of inhibitory postsynaptic currents recorded in pyramidal cells upon stimulation of presynaptic PV cells (WT=24 pairs, 11 mice; HET=13 pairs, 5 mice; P=0.69, Wilcoxon rank-sum test). (g) Amplitudes of excitatory postsynaptic currents recorded in PV cells upon stimulation of presynaptic pyramidal neurons (WT=20 pairs, 10 mice; HET=19 pairs, 6 mice; P=0.07, Wilcoxon rank-sum test). (h) Amplitudes of inhibitory postsynaptic currents recorded in PV cells upon stimulation of presynaptic PV cells (WT=20 pairs, 6 mice; HET=9 pairs, 3 mice; P=0.19, Wilcoxon rank-sum test). (i) Paired pulse ratios recorded in each of the three types of connections. All P-values >0.05, Wilcoxon rank-sum test. Plots in d–i are box plots. Red crosses identify major outliers.