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

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Accession:244599
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.
Reference:
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]
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:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Pacemaking mechanism; Temporal Pattern Generation; Oscillations; Extracellular Fields;
Implementer(s): Lopez-Jury, Luciana [lucianalopezjury at gmail.com]; 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;
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DAnotch_AIS
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TITLE calcium channels (L, N, and T types) 
 
UNITS {
       (molar) = (1/liter)
       (S)  = (siemens)
       (mA) = (milliamp)
       (mV) = (millivolt)
       (mM) = (millimolar)
        F = (faraday)  (coulomb)
        R = (mole k)   (mV-coulomb/degC)
       
}
 
NEURON {
        SUFFIX cachan
        USEION ca READ cai WRITE ica
        RANGE  gcalbar,gcanbar,gcahvabar,ica,ical,icahva,ican,kml,kmn
        GLOBAL dlinf,dhvainf,fhvainf
}
 
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
 
PARAMETER {
        v (mV)
        dt (ms)
        cai   (mM)
        celsius =  35.0      (degC)
        gcahvabar =  0.0e-6 (S/cm2)
        gcalbar =  11.196e-6  (S/cm2)
        kmn = 0.0001   (mM)
        kml = 0.00045  (mM)
        eca = 120 (mV)
        cao = 2.0 (mM)
        
}
 
STATE {
        dhva dl  fhva
}
 
ASSIGNED {
        ica (mA/cm2)
        ical (mA/cm2)
        ican (mA/cm2)
        icahva (mA/cm2)
        dlinf  dhvainf fhvainf 
 }
 
BREAKPOINT {
        SOLVE states METHOD cnexp
        ical = gcalbar*dl*(v - eca)
        icahva = gcahvabar*dhva*fhva*(v - eca)
        ica  = ical +  icahva
}
 
UNITSOFF
 
INITIAL {
        dl = boltz(v,-45.0,5.0)
        dhva = boltz(v,-10.0,10.0)
        fhva = boltz(v,-48.0,-5.0)
}

DERIVATIVE states {  :Computes state variables m, h, and n 
LOCAL dlinf,dhvainf,fhvainf,dltau,dhvatau,fhvatau
        dlinf = boltz(v,-45.0,5.0)
        dhvainf = boltz(v,-10.0,10.0)
        fhvainf = boltz(v,-48.0,-5.0)
        dltau = gaussian(v,18.0,25.0,70.0,0.30)
        dhvatau = gaussian(v,0.1,13.0,62.0,0.05)
        fhvatau = gaussian(v,0.5,18.0,55.6,0.5)
        dl'  = (dlinf-dl)/dltau
        dhva' = (dhvainf-dhva)/dhvatau
        fhva'  = (fhvainf-fhva)/fhvatau
}
 
 
FUNCTION gaussian(v,a,b,c,d) {
        LOCAL arg
        arg= a*exp(-(c+v)*(v+c)/(b*b)) +d
        gaussian = arg
}
 
 
FUNCTION boltz(x,y,z) {
               LOCAL arg
                arg= -(x-y)/z
                if (arg > 50) {boltz = 0}
                else {if (arg < -50) {boltz = 1}
                else {boltz = 1.0/(1.0 + exp(arg))}}
}

 
UNITSON


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