HCN hyperpolarization-activated cation channels inhibit EPSPs by interactions with M-type K(+) channels.
The processing of synaptic potentials by neuronal dendrites depends on both their passive cable properties and active voltage-gated channels, which can generate complex effects as a result of their nonlinear properties. We characterized the actions of HCN (hyperpolarization-activated cyclic nucleotide-gated cation) channels on dendritic processing of subthreshold excitatory postsynaptic potentials (EPSPs) in mouse CA1 hippocampal neurons. The HCN channels generated an excitatory inward current (I(h)) that exerted a direct depolarizing effect on the peak voltage of weak EPSPs, but produced a paradoxical hyperpolarizing effect on the peak voltage of stronger, but still subthreshold, EPSPs. Using a combined modeling and experimental approach, we found that the inhibitory action of I(h) was caused by its interaction with the delayed-rectifier M-type K(+) current. In this manner, I(h) can enhance spike firing in response to an EPSP when spike threshold is low and can inhibit firing when spike threshold is high.
Department of Neuroscience, Columbia University, New York, New York, USA.
Meena S
MS
George
L F
LF
Abbott
Steven A
SA
Siegelbaum
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D003198:Computer Simulation; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology*; D006624:Hippocampus / Q000502:physiology*; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D051657:KCNQ1 Potassium Channel / Q000502:physiology; D051379:Mice; D009924:Organ Culture Techniques; D015221:Potassium Channels / Q000502:physiology*; D017966:Pyramidal Cells / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*
D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D051657:KCNQ1 Potassium Channel; C496910:Kcnq1 protein, mouse; D015221:Potassium Channels