Figure 4.

HC-3 inhibits choline-induced current. A, HC-3 at 1 μm inhibits the choline-induced current (10 μm choline at −60 mV). Perfusion of 1 μm HC-3 alone reveals an apparent outward current (leak) in the transporter (white bar). There was no detectable leak current for control oocytes under the same conditions. A slow baseline drift was removed from A. B, I–V curves for 10 μm choline-induced current and 1 μm HC-3-revealed leak current were obtained from WT and LV mutants (n = 5). C, The ratio of choline-induced current to HC-3-revealed leak current is calculated from B. The ratio is constant at any voltage for either WT or LV. D, Leak current depolarizes oocytes. Resting potentials were assessed in water-injected control oocytes, WT-expressing oocytes, and LV-expressing oocytes in the absence of choline. Compared with the water-injected control oocytes, resting potentials in WT- and LV-expressing oocytes were significantly depolarized (n = 7).