Mg2+-evoked currents in Xenopus oocytes expressing hMagT1. Current-voltage relationships obtained from linear voltage steps from -150 mV to +25 mV in the presence of Mg2+-free solutions or those containing the indicated concentrations of MgCl2. Oocytes were clamped at a holding potential of -15 mV and stepped from -150 mV to +25 mV in 25 mV increments for 2 s at each of the concentrations indicated. Shown are average I-V curves obtained from control H2O-injected (n = 13) or MagT1-expressing (n =/>7) oocytes. Note, the positive shift in reversal potential, indicated by arrows, with increments in magnesium concentration. Values are mean ± SEM of observations measured at the end of each voltage sweep for the respective Mg2+ concentration.