Figure 3.

Low intracellular chloride speeds up the decay time. A, GlyR-mediated currents recorded from perforated vesicles permeabilized with the cation-permeable antibiotic gramicidin D (4 individual responses to a 1 ms 3 mm glycine applications separated by 1 min; successive responses shown as progressively lighter gray lines). Note the gradual decrease in the peak amplitude and the speeding up of the response decay with chloride depletion, shown in C and D for the patch of A. When the vesicle ruptured spontaneously (B), the intracellular chloride concentration was restored and the decay time was prolonged (compare scaled traces before and after rupture on the rightmost panel). Individual values (dots) and their average (bars) are shown in H, by the side of the cell-attached prediction (first column). The average time course of the peak current and decay time for 14 patches is shown in E and F. The effect on both peak and decay was much larger and progressed faster in patches with an initially high current (like the one shown in A), hence the reduced effect on peak and decay when many patches were averaged. Further confirmation of the chloride modulation was obtained by substituting the intracellular chloride with varying amounts of gluconate. Three patches recorded with different intracellular chloride concentrations are shown in G. Average decay time constants at each chloride concentration are represented by the bars in H (dots are individual experiments). The time course of deactivation calculated from the cell-attached rates (first column in H) is between those observed with 10 and 30 mm chloride in the pipette.