Figure 7.

I_Nap is already expressed in V1^R. A1, Representative trace of I_Nap evoked by a slow depolarizing voltage ramp in a V1^R (CsCl intracellular solution). I_Nap (black trace) was isolated by subtracting the current elicited by a voltage ramp (70 mV/s) in the presence of TTX (inset, green trace) from the control current (inset, black trace). TTX-sensitive current was blocked by 5 μm riluzole (red trace). Left, Inset shows the protocol to generate voltage-dependent slow inward currents in control conditions (black), after 5 μm riluzole application (red) or 1 μm TTX application (green). Right, Inset shows the current evoked by a depolarizing voltage step from −100 to 20 mV in the absence and in the presence of 5 μm riluzole. A2, Voltage dependence of I_Nap conductance calculated from the trace shown in A1. The activation curve was obtained by transforming the current evoked by a depolarizing voltage ramp from −100 to 20 mV (70 mV/s) using the following equation: G_NaP = − I_Nap/[(−V_h)+E_Na+] where V_h is the holding potential at time t during a depolarizing voltage ramp and E_Na+ is the equilibrium potential for sodium (E_Na+ = 60 mV). The G_NaP/V_h curve was fitted with a Boltzmann function (see Materials and Methods), where V_half is the V_h value for I_Nap half activation, k the slope factor of the curve and G_max the maximum conductance. B, Box plot showing G_max density in V1^R (n = 12). C, Box plots showing the variation of the percentage I_Nap block by 5 μm riluzole in V1^R.