Figure 1.

Nmb enhances I_T in TG neurons. A, left panel, representative recording from small TG neurons before and after 0.5 mM NiCl₂ (Ni²⁺) application. Currents were recorded by a 40 ms depolarizing step pulse from the holding potential of -110 mV or -60 mV to -40 mV. Inset: remaining current (I_T) after off-line subtraction. B, summary data indicate the inhibition of Ni²⁺ at 50 µM (n = 5) or 0.5 mM on I_T (n = 5). Ni²⁺ at 0.5 mM completely blocked I_T in TG neurons. C, time course (left panel) and summary data (right panel) show the effect of 100 nM Nmb on I_T (n = 9). Insets indicate the exemplary current traces. The Arabic numbers represent points used for representative traces. Ni²⁺ (0.5 mM) was applied at the end of each voltage-clamp recording to determine the current baseline. I_T were then calculated by digitally subtracting currents after Ni²⁺-treatment from those before application of NiCl₂. This protocol is used for calculation of pure I_T amplitude in all recordings. *p < 0.05 versus control, two-tailed t test. D, dose-dependent effects of Nmb on I_T. Solid line represents the sigmoidal dose-response fits. Numbers in parentheses denote n cells tested at each concentration. E, current-voltage (I-V) plots show the effect of 100 nM Nmb on the current density of T-type channels at each voltage (n = 8). Currents were elicited by test pulses that range from -80 mV to 0 mV in increments of +10 mV. F-G, application of 100 nM Nmb had no significant effect on the voltage-dependent activation curve (F), but shifted the steady-state inactivation curve towards a depolarizing direction (G). Insets, stimulation protocols. H, summary data show respective effects of Nmb (100 nM) on V_half of the activation (n = 9) and inactivation (n = 9) curves indicated in panels F and G, respectively. *p < 0.05 versus control, two-tailed t test.