NKCC1 controls the reversal potential of GABA
responses and resting membrane potential in migrating neuroblasts but not in GCs. (A) Reversal potential of muscimol-induced currents and resting membrane potential (RMP) in cells injected with control shRNA. (Ai) Upper panel: current traces showing the responses to a voltage-ramp protocol (bottom trace) applied to a RMS neuroblast recorded with the gramicidin-perforated patch technique. The ramp was induced in the absence (black) and presence (gray) of muscimol puffed near the soma of the recorded cell. The reversal potential was determined by fitting a straight line (light blue) to the subtracted current (middle trace). Scale top to bottom: 50 pA, 20 pA, 200 ms. Lower panel: high magnification version of the trace in the upper panel. Scale: 100 pA, 40 pA, 100 ms. (Aii) Average reversal potentials (left axis; dots) of the muscimol responses in migrating neuroblasts and GCs. The RMP (diamonds) is indicated on the right axis of the same plot. (Aiii) Driving force for muscimol responses in control neuroblasts and GCs. (B) Reversal potential to muscimol-induced current and RMP in cells with impaired NKCC1 function. (Bi) Current traces elicited by a voltage ramp applied to a migrating neuroblast transduced with shNKCC1 (as described in (A)). Scale: 100 pA, 50 pA, 200 ms. Lower panel: higher magnification of the upper panel trace. Scale: 100 pA, 60 pA, 100 ms. (Bii) Reversal potential (left axis) and RMP (right axis) measured in migrating neuroblasts and GCs after incubating slices with 10 μM bumetanide (dark blue) and in cells transduced with shNKCC1 (light blue). (Biii) Driving force of GABA-induced currents, for each cell type, after bumetanide treatment (dark blue) or in shNKCC1-expressing cells (light blue). (C) Plot of calculated average +/- sem [Cl-]i values in migrating neuroblasts and maturing GCs in control conditions (black), after incubation with bumetanide (dark blue), and in cells transduced with shNKCC1 (light blue).