Fig. 2.
Calcium-mediated conductances are responsible for the decrease in intrinsic excitability. (A) I-F plots in response to somatic current injection in control and Pten+/− (HET) neurons in presence of BAPTA (20 mM). Note there are no significant differences in firing rate in control–BAPTA (blue trace) versus Pten HET–BAPTA (red trace) neurons. Dotted lines represent control situation. (B) Input resistance recovery after BAPTA application. Note how the differences in IR are corrected with BAPTA in HET neurons (gray trace) without affecting control neurons (black trace). ANOVA test, Bonferroni post hoc test (*P < 0.05). (C) I-F plot in response to somatic current injection in control and HET neurons in presence of apamin (200 nM). Note there are no significant differences in firing rate between control–apamin (blue trace) and Pten HET–apamin (red trace) neurons after bath application of apamin. Dotted lines represent control situation. (D) Input resistance recovery after apamin bath application. Note how the differences in IR are corrected with apamin in HET neurons (gray trace) without affecting control neurons (black trace). ANOVA test, Bonferroni post hoc test (*P < 0.05). (E) No differences in AHP after SKCa channel blockade. Apamin decrease AHP in control (black trace) and HET (gray trace) neurons, suppressing previous differences in control situation. ANOVA test, Bonferroni post hoc test (**P < 0.01). (F, Left) Action potential average (30 ms) from control–apamin (blue trace) and Pten HET–apamin (red trace) neurons. (F, Right) Resized plot of boxed region showing average AHP traces from both genotypes. Note the same decreased AHP in control vs. HET. Dotted lines represent control situation. (G) Representative Western blot of cortical protein extracts made from control (WT) and Pten HET mice. Immunoblot was probed with PTEN and SK2 antibodies, as well as β-actin as a loading control. (H) Quantification of PTEN and SK2 proteins. Densitometry values indicate relative expression of PTEN and SK2 proteins, normalized to β-actin. (Pten HET: n = four mice; control; n = three mice; P < 0.05 Mann Whitney). In all traces, error bars indicate SEM.