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 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. ... 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. See paper for more and details.
Model Type: Neuron or other electrically excitable cell
Cell Type(s): Neocortex L5/6 pyramidal GLU cell
Currents: I h
Model Concept(s): Ion Channel Kinetics; Active Dendrites
Simulation Environment: NEURON
Implementer(s): Hallermann, Stefan [hallermann at medizin.uni-leipzig.de]
References:
Kole MH, Hallermann S, Stuart GJ. (2006). Single Ih channels in pyramidal neuron dendrites: properties, distribution, and impact on action potential output. The Journal of neuroscience : the official journal of the Society for Neuroscience. 26 [PubMed]