Article Figures & Data
Figures
- Figure 1.
Activity-blocked motoneurons have increased GABAergic mPSC amplitude that do not appear to be mediated by changes in total protein levels of GABAA subunits. A, GABAA mPSC amplitude was increased in activity-blocked motoneurons compared to controls, as shown in the averaged trace. B, Western blots from control and activity-blocked ventral spinal cords demonstrate no difference in total protein of either α1 or β2/3 GABAA subunits (normalized to actin protein levels).
- Figure 2.
ImPSC–V plots from motoneurons show that GABAergic mPSC conductance was no different in control and treated embryos, while EGABA was depolarized. A, mPSCs are shown at voltage steps of 20 mV increments in a motoneuron from an activity-blocked embryo. B, The average amplitude of GABAergic mPSCs at each step were then plotted against the step voltage. The graph is the average from all control and activity-blocked motoneurons. Error bars represent SE. C, Plots show GABAergic mPSC conductance (left) and reversal potentials (right) for several recorded cells (dots) from control (black) and activity-blocked (gray) embryos. Black line represents average values for cells.
- Figure 3.
Perforated patch recordings show a depolarizing shift in GABAergic reversal potential in motoneurons from activity-blocked embryos. Schematic shows puffing electrode adjacent to whole-cell recorded motoneuron. Trace shown of voltage-clamp recording using perforated patch electrode while picospritzing a GABAA agonist (isoguvacine, −60 mV). Two voltage ramps are applied (one before and the other during agonist application). Box expands image of ramp, which is composed of upward steps followed by a downward ramp. GABAergic I–V plots of control and activity-blocked motoneurons were generated by subtracting plots (isoguvacine − baseline). Plots are an average from 7 control and 7 activity-blocked embryos. Error bars represent SE.
- Figure 4.
The shift in EGABA was mediated by an increase in Cl− accumulation. A, The shift in EGABA was not mediated by a change in GABAA receptor HCO3− permeability. An ImPSC–V plot does not show significant shifts in EGABA before and after perfusing a 0 mm HCO3− extracellular solution (average of 4 cells). B, Enhanced Cl− accumulation in activity-blocked embryos was not due to changes in Cl− leak current. I–V plot constructed of a ramp from 0 mV to −90 mV. A linear fit of the data was made (−50 to −90 mV). Cl− conductance was not significantly different in control and activity-blocked embryos. Equations for fitted lines are shown, and these lines are extended (dashed line) to approximate the currents reversal potential. Error bars represent SE.
