title: Effects of calcium (Ca(2+)) extrusion mechanisms on electrophysiological properties in a hypoglossal motoneuron: insight from a mathematical model.
abstract: Spike-frequency dynamics and spike shape can provide insight into the types of ion channels present in any given neuron and give a sense for the precise response any neuron may have to a given input stimulus. Motoneuron firing frequency over time is especially important due to its direct effect on motor output. Of particular interest is intracellular Ca(2+), which exerts a powerful influence on both firing properties over time and spike shape. In order to better understand the cellular mechanisms for the regulation of intracellular Ca(2+) and their effect on spiking behavior, we have modified a computational model of an HM to include a variety of Ca(2+) handling processes. For the current study, a series of HM models that include Ca(2+) pumps, Na(+)/Ca(2+) exchangers, and a generic exponential decay of excess Ca(2+) were generated. Simulations from these models indicate that although each extrusion mechanism exerts a similar effect on voltage, the firing properties change distinctly with the inclusion of additional Ca(2+)-related mechanisms: BK channels, Ca(2+) buffering, and diffusion of [Ca(2+)]i modeled via a linear diffusion partial differential equation. While an exponential decay of Ca(2+) seems to adequately capture short-term changes in firing frequency seen in biological data, internal diffusion of Ca(2+) appears to be necessary for capturing longer term frequency changes.
authors.affiliation: Program in Neuroscience, Stony Brook University, Stony Brook, NY, USA; Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA.
authors.forename: Kyle G
authors.initials: KG
authors.lastname: Horn
authors.affiliation: Department of Physiology and Biophysics, Stony Brook University, Stony Brook, NY, USA. Electronic address: irene.solomon@stonybrook.edu.
authors.forename: Irene C
authors.initials: IC
authors.lastname: Solomon
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006801:Humans; D007002:Hypoglossal Nerve / Q000502:physiology*; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism; D008959:Models, Neurological; D008962:Models, Theoretical; D009046:Motor Neurons / Q000502:physiology*
chemical_list: D051036:Large-Conductance Calcium-Activated Potassium Channels; D002118:Calcium
keywords: BK channels; calcium buffering; calcium diffusion; calcium extrusion; computational models; hypoglossal motoneurons; intracellular calcium