Voltage-dependent properties of TTX-R Na⁺ currents induced by GTPγ-S and inflammatory soup in small DRG neurons. (A) Families of current traces evoked by 100-ms depolarizing voltage steps from -80 to +5 mV in 5-mV increments from −100 mV, 2 and 20 min after achieving the whole cell recording mode with internal GTPγ-S (500 μM). Difference current traces are shown for test potentials from −80 to −15 mV. (B) Current–voltage relationship of the experiment shown in A. TTX-R Na⁺ currents were measured either at the peak (circles) or 95 ms after the onset of the test pulse (diamonds). (C) Families of current traces evoked by 100-ms depolarizing voltage steps from −80 to −5 mV in 5-mV increments from −100 mV, before and 5 min after exposure to the inflammatory soup (50 nM BK, 500 nM PGE2, 1 μM His, 500 nM NE, 2 μM ATP). Difference current traces are shown for test potentials from −80 to −15 mV. (D) Current–voltage relationship of the experiment shown in C. TTX-R Na⁺ currents were measured either at the peak (circles) or 95 ms after the onset of the test pulse (diamonds). (E) Steady-state activation of NaN/Nav1.9 after fluoride (filled circles), GTPγ-S (open circles), and inflammatory soup (filled diamonds) had reached their maximum effects. Currents were studied using standard pulse protocol as in A and C. V_1/2 and k values were −44.5 ± 2 mV and 5.1 ± 0.5 mV (n = 6), −47 ± 1.5 mV and 5.3 ± 0.5 mV (n = 10), and −53 ± 1 mV and 5 ± 0.4 mV (n = 14) for the inflammatory soup, GTPγ-S, and fluoride conditions, respectively. Recordings made using the intracellular solution 3 (Table I; 130 mM CsCl, 0 mM CsF, 0 mM KCl).