Article Figures & Data
Figures
- Figure 1.
Stellate cells express Kv7-mediated M-current that can be blocked by 10 μm XE991. A, Representative whole-cell voltage-clamp recording from a layer II MEC SC, in response to the voltage command protocol indicated by the upper trace. The lower trace shows the tail current evoked by a repolarizing step to −64 mV in control (black) and after application of 10 μm XE991 (red). The bottom shows the XE991-sensitive current obtained by digital subtraction of the red trace (XE991) from the black trace (control). Ba,Time course of the effect of XE991 on the steady-state outward current (Iss) during the last 100 ms of a voltage step to −24 mV from a holding potential of −84 mV. Bb, Population data showing that XE991 reduced Iss; the effect was statistically significant. Ca, Time course of the effect of XE991 on the fast tail current (Itail) evoked by a voltage step to −64 mV. Cb, Population data showing a statistically significant effect of XE991 on Itail. D, Representative recordings showing the effect of 20 mm TEA on the tail current. Subsequent application of 10 μm XE991 had only a minor effect, suggesting that TEA blocks most of the Kv7/M-current in MEC SCs. Ea, Time course of the effect of TEA and XE991 on the Iss. Eb, Population data showing that TEA blocked most of the Kv7/M-current activated by the step to −24 mV, whereas the effect of XE991 was not statistically significant. Fa, Time course of the effect of TEA and XE991 on the Itail. Fb, Population data showing that TEA blocked most of the Kv7-mediated tail current and XE991 had only a minor and not statistically significant effect.
- Figure 2.
Effects of retigabine showed that MEC SCs express functional Kv7/M-channels. A, The Kv7/M-channels agonist retigabine (10 μm) decreased the cell input resistance (Rinput) and excitability. Subsequent application of XE991 (10 μm) reversed the effects of retigabine (n = 5). Figure 2A shows representative voltage responses to 1-s-long current steps (50 pA; control, black; retigabine, green; XE991, red). B, Representative traces of action potential trains elicited by depolarizing current steps in the three conditions tested. Retigabine strongly reduced the intrinsic excitability and its effects were reversed by application of XE991. C, Time course of the effects of retigabine and XE991. D, Effect of retigabine on the average f/I curve (n = 5), subsequent application of XE991 restored the cell excitability.
- Figure 3.
Kv7/M-channels contribute to excitability control in MEC SCs. A, Representative traces of spike trains in response to 1-s-long depolarizing current steps of 150 pA in normal medium (black) and after application of 10 μm XE991 (red). B, The mean spike frequency during the 1-s-long current steps was increased by XE991 (a) and the change was statistically significant (b). The effect of XE991 on the intrinsic excitability was evident throughout the whole range of stimulus intensities tested (Bc). C, Representative traces showing an expanded view of the first three (left) and last two (right) interspike intervals (ISIs) from the traces with a similar initial spike frequency (Finitial) in control (56.2 Hz) and XE991 (54.2 Hz). D, XE991 significantly reduced the adaptation index.
