Disentangling astroglial physiology with a realistic cell model in silico (Savtchenko et al 2018)

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Accession:243508
"Electrically non-excitable astroglia take up neurotransmitters, buffer extracellular K+ and generate Ca2+ signals that release molecular regulators of neural circuitry. The underlying machinery remains enigmatic, mainly because the sponge-like astrocyte morphology has been difficult to access experimentally or explore theoretically. Here, we systematically incorporate multi-scale, tri-dimensional astroglial architecture into a realistic multi-compartmental cell model, which we constrain by empirical tests and integrate into the NEURON computational biophysical environment. This approach is implemented as a flexible astrocyte-model builder ASTRO. As a proof-of-concept, we explore an in silico astrocyte to evaluate basic cell physiology features inaccessible experimentally. ..."
Reference:
1 . Savtchenko LP, Bard L, Jensen TP, Reynolds JP, Kraev I, Medvedev N, Stewart MG, Henneberger C, Rusakov DA (2018) Disentangling astroglial physiology with a realistic cell model in silico. Nat Commun 9:3554 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Glia;
Brain Region(s)/Organism: Hippocampus;
Cell Type(s): Astrocyte;
Channel(s): I Calcium; I Potassium; Kir;
Gap Junctions: Gap junctions;
Receptor(s):
Gene(s):
Transmitter(s): Glutamate;
Simulation Environment: NEURON; MATLAB; C or C++ program;
Model Concept(s): Calcium waves; Calcium dynamics; Potassium buffering; Volume transmission; Membrane Properties;
Implementer(s): Savtchenko, Leonid P [leonid.savtchenko at ucl.ac.uk];
Search NeuronDB for information about:  I Calcium; I Potassium; Kir; Glutamate;
COMMENT
Uses electroneutral, exponentially decaying IP3 source 
to emulate effect of activating bradykinin receptors on IP3.
Equivalent to approach used by Fink et al. 2000 
to represent bradykinin action.
ENDCOMMENT

NEURON {
  SUFFIX bkr
  USEION ip3 WRITE iip3 VALENCE 1
  NONSPECIFIC_CURRENT ix
  RANGE jbar, beta, j, i
  GLOBAL del
}

UNITS {
  (um)    = (micron)
  (molar) = (1/liter)
  (uM)    = (micromolar)
  (mA)	  = (milliamp)
  FARADAY = (faraday)  (coulomb)
}

PARAMETER {
  del (ms)  : time at which it starts

  k = 1.188e-3 (/ms) : k0

  jbar = 20.86 (uM um/s) : J0  flux at onset
  beta = 1 (1) : scale factor for local variation of bradykinin receptor density
}

ASSIGNED {
  jip3 (micro/um2 ms) : IP3 flux generated at membrane in micromoles/um2 ms
  iip3 (mA/cm2) : ip3 current
  ix   (mA/cm2) : to cancel out polarizing effect of the ip3 current
}

INITIAL {
  jip3 = 0
  iip3 = 0
  ix = 0
}

BREAKPOINT {
  at_time(del) : when it turns on
  at_time(del + (10/k)) : when to stop calculating very small exponentials

: produced at inner surface of membrane upon application of bradykinin
  if (t > del && t <= del + (10/k)) {
    jip3 = (1e-18)*beta*jbar*exp(-k*(t-del))
  }else{
    jip3 = 0
  }

  iip3 = -(1e8)*jip3*FARADAY
  ix = -iip3
}

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