Fig. 4
Neurons lacking FMRP have reduced INaP densities, and their burst properties are insensitive to riluzole. A Persistent sodium currents (INaP) evoked by a slow depolarizing ramp (−100 to −20 mV, 20 mV/s) either before (traces a) or during (traces b) application of TTX. The TTX-sensitive current (traces c) was isolated by subtracting traces a and b. B I–V curves plotted from the ramp-evoked INaP, showing the decreased INaP in neurons lacking FMRP. Currents are normalized to the corresponding cell capacitance. C Quantification of current density at −20 mV show significant decrease of the persistent sodium current in neurons lacking FMRP. Overall, the mean current densities are −1.44 ± 0.17 (FMR1+/y, n = 18, N = 3); −1.73 ± 0.33 (CON2, n = 10, N = 3); −0.27 ± 0.03 (FMR1−/y, n = 18, N = 3); −0.35 ± 0.098 (FXS3, n = 9, N = 3). **p < 0.01, ***p < 0.001, two-way repeated measures ANOVA with post hoc Tukey’s test, paired t test and Wilcoxon test. D Representative traces illustrating spontaneous bursts recorded from either a FMR1+/y neuron or a FMR1−/y neuron before and after the application of riluzole (0.1 μM). E Quantification of the number of bursts recorded from FMR1+/y, CON2, FMR1−/y, or FXS3 neurons before (open symbols) or after (closed symbols) application of riluzole. Overall, the mean number of bursts recorded are 5.733 ± 0.72 (FMR1+/y, n = 15, N = 3); 5.733 ± 0.65 (FMR1+/y + riluzole, n = 15, N = 3); 6.3 ± 0.9 (CON2, n = 10, N = 3); 7 ± 1.12 (CON2 + riluzole, n = 10, N = 3); 42.33 ± 8.92 (FMR1−/y, n = 9, N = 3); 38.89 ± 8.49 (FMR1−/y + riluzole, n = 9, N = 3); 34.1 ± 9.52 (FXS3, n = 10, N = 3); 34.3 ± 9.62 (FXS3 + riluzole, n = 10, N = 3). F Quantification of the duration of bursts recorded from FMR1+/y , CON2, FMR1−/y, or FXS3 neurons before (open symbols) or after (closed symbols) application of riluzole. Overall, the mean burst durations are 47.86 ± 6.27 s (FMR1+/y); 14.14 ± 1.33 s (FMR1+/y + riluzole); 47.81 ± 12.14 s (CON2); 25.55 ± 9.54 s (CON2 + riluzole); 8.77 ± 1.34 s (FMR1−/y ); 9.43 ± 1.62 s (FMR1−/y + riluzole); 8.91 ± 2.19 s (FXS3); 9.01 ± 2.52 (FXS3 + riluzole) **p < 0.01; ***p < 0.001, paired t test, Wilcoxon test