Figure 8. Effect of intracellular magnesium on WT, R539W and R539F mutant channels, and after membrane cholesterol depletion.

A, C, E, relative tail-current amplitude (at −40 mV) of WT or mutant channels measured after a depolarization to +80 mV plotted against time during a 1.1 mmol/L free Mg²⁺ application on a giant-patch. Start-to-start interval = 2 s. Current values are normalized to the current level measured before magnesium application (time 0). Cholesterol depletion was induced by 1 hour of 2 mmol/L cyclodextrin (cyclo) or 24 hours of 10 µmol/L triparanol (tripa) pre-treatment. B, D, F, mean rundown time constant (τ) of WT and mutant channels (B), and with and without 2 mmol/L cyclodextrin (D, n = 9–13) or 10 µmol/L triparanol (F, n = 9–15). *p<0.05, **p<0.01 versus WT. DMSO in which triparanol was diluted (E and F) has an effect on rundown kinetics (τ = 15.4±1.6, n = 7 versus τ = 35.0±3.65, n = 15, without and with DMSO pre-treatment respectively, p<0.01).