Backward swimming duration after depolarization in tetraethylammonium chloride (TEA) with Na+, TEA with Mg2+, or KCl. Durations of backward swimming (sec) in buffers with: (A) 25 mM TEA with 10 mM NaCl, (B) 25 mM TEA with 5 mM MgCl2; and (C) 30 mM KCl. Data are normalized to the control backward swimming duration. Asterisks denote significant difference from control using the Mann–Whitney U-test (*P < 0.05; **P < 0.0001). Data are averages from three experiments; n = 45 to 418 (A); 45 to 165 cells (B) and 25 to 240 (C). Data are averages ± standard error of the mean (SEM).