Fig. 1.
Current carried by QX-314 in transient receptor potential vanilloid 1 protein (TRPV1) channels expressed in N1E-115 cells. A: currents evoked by voltage ramps (inset) before and after application of 1 μM capsaicin in an external solution with QX-314 as the sole cation (10 mM QX-314-hydroxide, 277 mM sucrose, 5 mM HEPES, pH adjusted to 7.4 with HCl). Internal solution was 135 mM CsCl, 5 mM EGTA, 10 mM HEPES, pH adjusted to 7.2 with ∼8 mM CsOH. Currents from the downward-going ramp were averaged from 10 sweeps each, before and after application of capsaicin, and plotted as current vs. voltage. Vrev, reversal potential. B: TRPV1 currents with external solutions containing either 10 or 20 mM QX-314 vs. a Cs-based internal solution (different cell than A). Solutions as in A, with the 20 mM QX-314 solution consisting of 20 mM QX-314-hydroxide, 250 mM sucrose, 5 mM HEPES, pH adjusted to 7.4 with HCl. Capsaicin-activated current is plotted (subtraction of currents before and after application of 1 μM capsaicin with 5 sweeps signal-averaged in each condition). C: same as B but with an N-methyl-d-glucamine (NMDG)-based internal solution (135 mM NMDG, 5 mM EGTA, 10 mM HEPES, pH adjusted to 7.2 with HCl).