A Dynamic Computational Study of the Role of Ion Channels in a Neuron

Eric John Hall

Abstract


Neurons are specialized cells that exchange information across connections, called synapses, using electrical signals.  These signals are formed by a potential difference (a voltage) across the cell membrane.  This voltage changes as ion channels, specialized protein pores, open and close to allow ions to flow across the membrane.  The region of a neuron which typically receives signals is called the dendrite. Synaptic signals propagate along the dendrite to the cell body, or soma. The soma adds together all the individual synaptic signals in a process called synaptic integration.   It is expected that as synaptic input is added to a neuron, the effect of each additional input on the integration process will be less than the previous input.  However, a process known as linear synaptic integration is observed, whereby additional synaptic inputs have the same effect as the previous inputs.  Linear synaptic integration is possible due to the presence of voltage-gated ion channels that modify the strength of these synaptic signals.  The goal of this research is to study the role of three types of dendritic voltage-gated ion channels in the context of linear synaptic integration.  We constructed a time-dependent computational model of a single dendritic compartment using available physiological data.  We studied the effect of the voltage-gated ion channels individually and in combinations to identify the conditions required for linearization.  Physiological studies have shown that neurons express different types of ion channels in varying amounts in different regions of the neuron.  Our results help demonstrate one possible reason why this occurs: individual channels and their combinations are active at different levels of synaptic activity and over different voltage ranges.  By utilizing multiple types of ion channels, the neuron is able to function under a much greater range of conditions.  By expressing the right combination of voltage-gated ion channels, the neuron can achieve linear synaptic integration over the entire voltage range between rest and threshold.


Keywords


Synaptic Integration; Voltage-gated Ion Channels

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