Inflammatory soup potentiates NaN/Nav1.9 current and lowers the threshold of excitability using a KCl-based intracellular solution. (A) Families of superimposed membrane potential changes evoked by a series of current pulse injection in Nav1.9+/+ neuron before (left) and 3 min after the application of inflammatory soup (right). (B) Membrane potential values (collected isochronally 60 ms after the onset) plotted as a function of injected currents from the experiment shown in A. Note that injected current caused linear responses in control condition (open circle) and active depolarization in the presence of the inflammatory soup (filled circle). (right inset) Expanded traces from A showing the reduced first spike latency in the presence of the inflammatory soup (filled circle). (left inset) Mean first spike latency before (93 ± 9 ms) and during (43 ± 7 ms) the superfusion of inflammatory soup (n = 12; **, P < 0.01 paired t test). (C) Whole-cell currents elicited in the Nav1.9+/+ neuron shown in A by a 3.3-s ramp depolarization from −100 to 20 mV (rate, 36 mV s−1) before and during the superfusion of the inflammatory soup (one trace every 10 s). The bottom panel shows the inflammatory soup–induced current obtained by subtraction. Note that inflammatory soup potentiates the NaN/Nav1.9 current and inhibits an outward potassium current. Recordings made using the intracellular solution 5 (Table I; 0 mM CsCl, 0 mM CsF, 130 mM KCl).
