Fig. 7: Effects of Navβ4 C-terminal peptide (β4-WT) on I_NaR and excitability of RAPNs in 20 dph males.

a, b Representative traces of I_NaT elicited at +30 mV followed by I_NaR elicited at −30 mV immediately after (black) and 7 min after (red) achieving whole-cell configuration with β4-WT (KKLITFILKKTREK) in the patch pipette. The regions in the red dashed boxes are enlarged in the insets. c Time-dependent increase in the normalized I_NaR to I_NaT ratio caused by β4-WT, measured at the −30 mV test potential in individual RAPNs (mean ± SEM in black); two-tailed paired t test, N = 10 RAPNs. d Representative traces of I_NaT elicited at +30 mV followed by I_NaR elicited at −30 mV immediately after (black) and 7 min after (blue) achieving whole-cell configuration with β4-Scr (KIKIRFKTKTLELK) in the patch pipette. The region in the red dashed box is enlarged in the inset_. e Lack of time-dependent increase in normalized I_NaR to I_NaT ratio by β4-Scr, measured at the −30 mV test potential in individual RAPNs (mean ± SEM in black); paired t test, N = 9 RAPNs. f Fold changes in normalized I_NaR to I_NaT ratio between 0 and 7 min for RAPNs exposed to β4-WT or β4-Scr in the patch pipette; two-tailed Student’s t test; N = 10 and 9 RAPNs for β4-WT and β4-Scr, respectively. Data are presented as individual data points with bars as mean values ± SEM. g Representative traces of the first APs elicited by a +300 pA current injection at four-time points after entering the whole-cell configuration with β4-WT in the patch pipette; the APs are aligned at their peak. h Phase plane plots from the first elicited AP recorded immediately (black) or 15 min (red) after entering the whole-cell configuration in cells exposed to β4-WT. The blue arrows in g and h point respectively to the spikelet and resulting alteration in the repolarization rate in the phase plane plot. i Time-dependent effects of β4-WT on the 1st AP half-width in individual cells (mean ± SEM in black; two-tailed paired t test; N = 12 RAPNs). j Representative traces of the first APs elicited by a +300 pA current injection at four-time points after entering the whole-cell configuration with β4-Scr in the patch pipette; the APs are aligned at their peak. k Phase plane plots from the first elicited AP recorded immediately (black) or 15 min (red) after entering the whole-cell configuration for cells perfused with the β4-Scr. l Time-dependent effects of β4-Scr on the 1st AP half-width in individual cells (mean ± SEM in black; two-tailed paired t test; N = 15 RAPNs).