Figure 3

TWIK-1 deficiency causes enhanced intrinsic excitability of dentate granule cells. (A) Representative response of membrane potential to stepwise current injections (left panel). The current was injected into cells in 25 pA steps starting from -120 pA and up to 55 pA (1.2 sec step duration). Input-output properties of naïve (n = 36 cells), Sc shRNA (n = 32 cells) or TWIK-1 shRNA (n = 30 cells) expressing granule cells measured as the number of spikes vs. injected current intensity (right panel). (B) Distribution of cells according to excitability patterns. Plotted are percentage of cells with binned number of spikes fired during a 30 pA injected current step. (C) Representative response of membrane potential to stepwise current injections (left panel). Averaged response of membrane potential to stepwise current injection in naïve (n = 27 cells), Sc shRNA (n = 20 cells) or TWIK-1 shRNA (n = 21 cells) expressing cells (right panel). The RMP of cells was maintained at -70 mV. Current injection into the cell body was performed stepwise from -30 pA to 90 pA, in 5 pA steps. The solid lines are an exponential fit of the data plots. Dotted line indicates the spiking threshold level. (D) Representative traces of rheobase current measurements (left panel). The RMP of cells was kept at -70 mV and then depolarizing current was injected stepwise, in 2 pA steps until the membrane potential reached the firing threshold (red traces). Averaged values of rheobase currents in naïve (n = 12 cells), Sc shRNA (n = 13 cells) or TWIK-1 shRNA (n = 12 cells) expressing cells (right panel). All data are represented as mean ± S.E.M; *P < 0.05, **P < 0.01 Student's unpaired t-test.