FIG. 12.

Hyperpolarization-activated cyclic nucleotide (HCN)-gated channels enforce dendritic synaptic integration. A: simultaneous somatic (black traces) and dendritic (550 μm from the soma, gray traces) voltage recordings of action potential output evoked by the injection of barrages of EPSCs (bottom traces) at distal apical dendritic sites under control and in the presence of ZD 7288 (20 μM) in a P27 layer 5 pyramidal neuron. B: averaged action potential waveforms recorded from somatic (black) and apical dendritic sites (gray) under control (top traces) and in ZD 7288. Action potentials were aligned at the peak of somatically recorded events and averaged for all events generated across current-discharge relationship. Under control the somatic action potential was preceded by a dendritic spike, while in ZD 7288 somatic action potentials were followed by dendritic back-propagating action potentials. Data from the same cell as A. C: blockade of HCN channels transforms the current-discharge relationship evoked by barrages of distal apical dendritic simulated synaptic current. Data has been averaged from 6 neurons (P27–29). D: the percentage of action potentials driven by dendritic spikes under control and in the presence of ZD 7288.