Figure 7.
Turgor pressure does not affect membrane potential (Vm or Vi-o) dependence of gap junctions in Hensen cells. (A) Voltage stimulus protocols for each cell and current trace recorded in cell 2 are plotted (only five traces are shown for clarity). Each cell in a Hensen cell pair was separately voltage clamped at the same holding potential of −80 mV. Voltage steps from −140 to 70 mV for 100 ms in 10-mV increments were simultaneously delivered into both cells except for 10 mV, 10-ms test pulses superimposed on cell 1 only. Transjunctional current (I j) is measured in cell 2. The turgor pressure of cell 1 was directly changed by the patch pipette. Three current traces from cell 2 at different pressures were zeroed and superimposed in the middle. (B) Positive turgor pressure decreased G j at all membrane potentials. Note G j decrease as the cells were depolarized. R s at 0 kPa, 12.5 MΩ; at 1.2 kPa, 12.7 MΩ; at 2 kPa, 12.2 MΩ.