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.
George
Meena S
MS
Department of Neuroscience, Columbia University, New York, New York, USA.
Abbott
L F
LF
Siegelbaum
Steven A
SA
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