Single Ih Channels in Pyramidal Neuron Dendrites: Properties, Distribution, and Impact on Action Potential Output.
From: Division of Neuroscience, John Curtin School of Medical Research, Australian National University, Canberra 0200, Australian Capital Territory, Australia. maarten.kole@anu.edu.au
The Journal of neuroscience : the official journal of the Society for Neuroscience
- Publish Date: Feb 2006
- ISSN: 1529-2401
- Volume: 26
- Issue: 6
- Pages: 1677-87
- Medium: Internet
- Language: English
- Citation (JAMA): Kole Maarten H P, Hallermann Stefan, Stuart Greg J, et al. Single Ih Channels in Pyramidal Neuron Dendrites: Properties, Distribution, and Impact on Action Potential Output.. J. Neurosci. Feb 2006;26:1677-87
Abstract
The hyperpolarization-activated cation current (Ih) plays an important role in regulating neuronal excitability, yet its native single-channel properties in the brain are essentially unknown. Here we use variance-mean analysis to study the properties of single Ih channels in the apical dendrites of cortical layer 5 pyramidal neurons in vitro. In these neurons, we find that Ih channels have an average unitary conductance of 680 +/- 30 fS (n = 18). Spectral analysis of simulated and native Ih channels showed that there is little or no channel flicker below 5 kHz. In contrast to the uniformly distributed single-channel conductance, Ih channel number increases exponentially with distance, reaching densities as high as approximately 550 channels/microm2 at distal dendritic sites. These high channel densities generate significant membrane voltage noise. By incorporating a stochastic model of Ih single-channel gating into a morphologically realistic model of a layer 5 neuron, we show that this channel noise is higher in distal dendritic compartments and increased threefold with a 10-fold increased single-channel conductance (6.8 pS) but constant Ih current density. In addition, we demonstrate that voltage fluctuations attributable to stochastic Ih channel gating impact on action potential output, with greater spike-timing precision in models with the experimentally determined single-channel conductance. These data suggest that, in the face of high current densities, the small single-channel conductance of Ih is critical for maintaining the fidelity of action potential output.
Mesh Headings (Keywords): Action Potentials, Animals, Dendrites, Ion Channels, Male, Patch-Clamp Techniques, Pyramidal Cells, Rats, Rats, Wistar, Reproducibility of Results
Check for Full Text / PubMed Unique Identifier (PMID): 16467515
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