Computational Modeling of H Channel Currents in Rat Layer V Pyramidal Neurons

In layer V pyramidal neurons, neurons that project across the corpus callosum have different electrophysiological properties compared to neurons that project down to the pons. Hyperpolarization activated cyclic nucleotide gated (HCN) channels are thought to be the basis of this difference. Characterizing how HCN channel influence these electrophysiological differences may be key in determining how neurons perform memory tasks. To determine the role of HCN in these neuronal cells, these cells are injected with biotin, fixed and visualized under a microscope. After tracing these cells using the Neurolucida program, the cell parameters are imported into NEURON and modeled with any hypothetical channel. We use these tracings or reconstructions as well as cylinder representations of our cell measurements to determine the effect of HCN channels on input resistance, time constant and resonance. Our data from our model is consistent with our hypothesis that the presence of HCN channels decrease the input resistance and time constant. However we cannot establish that HCN channels are the basis for the electrophysiological differences between layer V pyramidal neurons as changes to the morphology of corticopontine neurons can produce the same electrophysiological differences.