Figure 5. I_Leak conducted by the U-type channel in RPeD1 cells is carried by Na⁺ ions.

(A1) Representative voltage traces of naïve control, control dsRNA/siRNA, and U-type dsRNA/siRNA 1 & 2 with and without Na⁺ free saline perfusion. (A2) Average voltage difference between Na⁺ free perfusion and saline perfusion for naïve control (n = 9), control dsRNA (n = 6), U-type dsRNA (n = 6), control siRNA (n = 6), U-type siRNA 1 (n = 6), U-type siRNA 2 (n = 4). (B1) Representative I_Leak in RPeD1 cells from naïve control, control dsRNA/siRNA, and U-type dsRNA/siRNA 1&2, at hyperpolarizing voltages in saline or Na⁺ free solution (B2) Representative I_Leak density-voltage (I–V) relations of naïve control, control dsRNA/siRNA, and U-type dsRNA/siRNA 1&2 in saline or Na⁺ free solution. (B3) comparison of the average normalized I_Leak in Na⁺ free solution over saline at −160 mV, −110 mV, and −60 mV for naïve control (n = 8), control dsRNA (n = 6), U-type dsRNA (n = 7), control siRNA (n = 4), U-type siRNA 1 (n = 4), and U-type siRNA 2 (n = 4). A significant reduction in normalized I_Leak under Na⁺ free condition was observed in RPeD1 cells from the naïve control and control dsRNA/siRNA groups, but not from U-type dsRNA/siRNA groups. All significant difference (P<0.05) between Na⁺ free saline current normalized to saline is denoted by *. The dashed line represents the current activity in saline. (C) Application of 100 µM TTX did not significantly affect I_leak. (C1) Representative leak current traces of naive control neurons in saline, 100 µM TTX, and saline wash under a hyperpolarizing step voltage protocol. (C2) Representative current-voltage relation for the leak current observed in saline, 100 µM TTX, and saline wash. Line represents a linear fit. (C3) Summary of relative current density of 100 µM TTX normalized to that in saline at various hyperpolarizing voltages: −160 mV (n = 5), −110 mV (n = 5) and −60 mV (n = 5). No significant difference was observed in the normalized currents among all the groups.