Figure 2.

Whole cell recordings from CA1 pyramidal apical dendrites show that h-current alterations are not solely responsible for hyperexcitability. (A) Whole cell, current clamp recordings of control (left) and HT (right) dendrite responses to 1500 ms long current injections from RMP. Recording distance 200 μm from soma. (B) Number of action potentials fired in response to 1500 ms depolarizing current injections in control (open squares) and HT (filled circles) dendrites from the RMP. (C) Number of action potentials fired in response to 1500 ms depolarizing current injections in control (open squares) and HT (filled circles) dendrites from a −60 mV holding potential. Insets: Number of action potentials in the first 300 ms of the depolarizing current injections. Note that the data in (B) and (C) are from the same population of dendrites, before and after compensation of the RMP difference by constant current injection. (D) Whole cell, current clamp recordings of control (top) and HT (bottom) dendrite responses to 1500 ms long current injections (recording distance: 200 μm) in the presence of 1 μM TTX, from a −60 mV holding potential. (E) Steady-state voltage deflection of control (open squares) and HT (filled circles) dendrites in response to 1500 ms current injections from a −60 mV holding potential. (F) Action potentials fired (% of control) in control (open squares) and HT (filled circles) dendrites in the presence of ZD7288, from RMP (left) and from a −70 mV holding potential (right; recording distance: 200 μm). (G) RMP of control (white bars) and HT (black bars) dendrites in the absence or presence of ZD7288. (H) Control and HT dendritic responses to artificial EPSPs generated by current injection from the recording pipette (recording distance: 200 μm) from RMP. (I) Average number of action potentials fired in response to the artificial EPSPs in (H).