Scorpion β-toxin Tz1 enhances or inhibits the activity of NaV channels in a subtype-specific and use-dependent manner. (A) Action potential–like voltage protocol used to elicit current responses from HEK 293 cells transiently expressing NaV1.4 or NaV1.5 channels. Successive trains of 20 individual pulses were applied at frequencies of 0.1 and 2 Hz. (B) Representative current traces of NaV1.4 (left) and NaV1.5 (right) channels, each obtained from the last stimulation of a train of 20 pulses before (ctrl) and after the application of 5 µM Tz1 (Tz1) for the indicated stimulation frequencies. Gray shaded areas visualize current integrals, and dashed lines indicate current responses under control conditions. (C) Mean integrals for NaV1.4 (n = 5) and NaV1.5 (n = 7) in the absence (ctrl) and presence of Tz1, normalized to the integrals under control conditions as a function of the pulse number. Horizontal bars indicate stimulation frequencies and the presence of 5 µM Tz1.
