Determinants of the intracellular and extracellular waveforms in DA neurons (Lopez-Jury et al 2018)

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To systematically address the contribution of AIS, dendritic and somatic compartments to shaping the two-component action potentials (APs), we modeled APs of male mouse and rat dopaminergic neurons. A parsimonious two-domain model, with high (AIS) and lower (dendro-somatic) Na+ conductance, reproduced the notch in the temporal derivatives, but not in the extracellular APs, regardless of morphology. The notch was only revealed when somatic active currents were reduced, constraining the model to three domains. Thus, an initial AIS spike is followed by an actively generated spike by the axon-bearing dendrite (ABD), in turn followed mostly passively by the soma. Larger AISs and thinner ABD (but not soma-to-AIS distance) accentuate the AIS component.
1 . López-Jury L, Meza RC, Brown MTC, Henny P, Canavier CC (2018) Morphological and Biophysical Determinants of the Intracellular and Extracellular Waveforms in Nigral Dopaminergic Neurons: A Computational Study. J Neurosci 38:8295-8310 [PubMed]
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Model Information (Click on a link to find other models with that property)
Model Type: Extracellular; Dendrite; Neuron or other electrically excitable cell;
Brain Region(s)/Organism: Basal ganglia;
Cell Type(s): Substantia nigra pars compacta DA cell;
Channel(s): I Calcium; I K,Ca; Na/K pump; I L high threshold; I T low threshold; I A; I N; I Na,t; I K;
Gap Junctions:
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Pacemaking mechanism; Temporal Pattern Generation; Oscillations; Extracellular Fields;
Implementer(s): Lopez-Jury, Luciana [lucianalopezjury at]; Canavier, CC;
Search NeuronDB for information about:  Substantia nigra pars compacta DA cell; I Na,t; I L high threshold; I N; I T low threshold; I A; I K; I K,Ca; I Calcium; Na/K pump;
cabal.mod *
nabalan.mod *
newcachan.mod *
newkca.mod *
pump.mod *
anatscale.hoc *
field.hoc *
fixnseg.hoc *
interpxyz.hoc *
setpointers.hoc *
// $Id: initxrec.hoc,v 1.2 2005/09/10 23:02:15 ted Exp $
// extracellular recording from model subjected to intracellular stimulation

load_file("") // specifies anatomical and biophysical properties of the cell
  // For this example, the file recreates CellBuilder
  // but it could also be a plain old hoc file.
  // This file must do the following:
  // 1.  create and connect the sections, and use a single access statement
  //     to declare one of them as the default section
  // 2.  assign biophysical properties and specify discretization,
  //     insert whatever density ("distributed") mechanisms are necessary.
  // 3.  insert extracellular and xtra into all sections that are to "feel" 
  //     the effect of an extracellular field. The parameters of extracellular 
  //     should be assigned the following values:
  //     xraxial=1e+09 xg=1e+09 xc=0 e_extracellular=0
  // 4.  if geometry was specified with the stylized method (i.e. L and diam)
  //     rather than the pt3d method, call define_shape(). Once is enough.
  //     Note that stylized models make sense only if they are 1 dimensional
  //     i.e. unbranched, with all sections lying along a straight line.
  //     This is because section orientation of branched stylized models
  //     is chosen automatically by NEURON, therefore has nothing to do
  //     with biological neurons or the modeler's possible intent to approximate
  //     the shape of a particular cell.
// load_file("initcell.hoc") // for the demo cell
// activesoma.hoc doesn't insert extracellular or xtra, so do it here
forall {
  insert extracellular
  xraxial = 1e9
  xg = 1e9
  xc = 0
  e_extracellular = 0
  insert xtra
load_file("anatscale.hoc")	// show xyz scale bars
load_file("interpxyz.hoc")	// only interpolates sections that have extracellular
load_file("setpointers.hoc")	// automatically calls grindaway() in interpxyz.hoc
load_file("")		// RunControl, graphs of v, vext, e_extracellular
// load_file("")		// graph of er_xtra, just for diagnostic|development purposes
load_file("field.hoc")		// computes extracellularly recorded potential vrec
load_file("")		// graph of vrec(t)
load_file("calcrxc.hoc")	// computes transfer r between segments and recording electrodes
                          // may require modification for particular electrode geometries
load_file("")	// intracellular stimulus
IClamp[0].del = 1e9
load_file("")  // specify adaptive integration
tstop = 2000 // long enough to see the first spike
tstop_changed() // rescale x axes

load_file("msgic.hoc")		// minimal hints