CA1 pyramidal cell: reconstructed axonal arbor and failures at weak gap junctions (Vladimirov 2011)

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Accession:144401
Model of pyramidal CA1 cells connected by gap junctions in their axons. Cell geometry is based on anatomical reconstruction of rat CA1 cell (NeuroMorpho.Org ID: NMO_00927) with long axonal arbor. Model init_2cells.hoc shows failures of second spike propagation in a spike doublet, depending on conductance of an axonal gap junction. Model init_ring.hoc shows that spike failure result in reentrant oscillations of a spike in a loop of axons connected by gap junctions, where one gap junction is weak. The paper shows that in random networks of axons connected by gap junctions, oscillations are driven by single pacemaker loop of axons. The shortest loop, around which a spike can travel, is the most likely pacemaker. This principle allows us to predict the frequency of oscillations from network connectivity and visa versa. We propose that this type of oscillations corresponds to so-called fast ripples in epileptic hippocampus.
Reference:
1 . Vladimirov N, Tu Y, Traub RD (2012) Shortest Loops are Pacemakers in Random Networks of Electrically Coupled Axons. Front Comput Neurosci 6:17 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Realistic Network; Axon;
Brain Region(s)/Organism: Hippocampus;
Cell Type(s): Hippocampus CA1 pyramidal GLU cell;
Channel(s): I Na,t; I A; I K; I M; I K,Ca; I Calcium; I Potassium;
Gap Junctions: Gap junctions;
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Oscillations; Axonal Action Potentials; Epilepsy; Conduction failure;
Implementer(s): Vladimirov, Nikita ;
Search NeuronDB for information about:  Hippocampus CA1 pyramidal GLU cell; I Na,t; I A; I K; I M; I K,Ca; I Calcium; I Potassium;
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VladimirovTuTraub2012
readme.html
bias.mod *
cad.mod *
cal.mod *
gap.mod *
ipulse1.mod *
ka.mod *
kahp.mod *
kc.mod *
kdr.mod *
km.mod *
naf.mod *
2cellsGUI.ses
cellTemplate.hoc
gapjunction.hoc
init_2cells.hoc
init_ring.hoc
mosinit.hoc
ringGUI.ses
screenshot1.jpg
screenshot2.jpg
screenshot3.jpg
                            
// This file runs 2 pyramidal cells connected by axonal gap junction 
// The gap junction is placed in axonal section 4, at 370 um from soma in each cell

load_file ("nrngui.hoc")
load_file("cellTemplate.hoc")
load_file("gapjunction.hoc")

tstop=15
ncells=2
ngaps=1
gj_conductance=3e-3 //[mcS]
// position of gj in axonal sections:
axonal_section1=4 // section index in cell[1].axon[]
axonal_section2=4 // section index in cell[2].axon[]
section1_pos=0.5 // position within section1
section2_pos=0.5 // position within section2
objectvar cells, gap

proc mkcells(){ local i localobj cell_
   cells=new List()
   for i=0,$1-1{
     cell_=new pyramidal()
	 cells.append(cell_)
   }
}
proc setpositions(){ local i, x, y
  for i=1,cells.count(){
      x=i*$1
	  y=i*$2
	  cells.object(i-1).position(x,y,0)
	  cells.object(i-1).setgid(i)
  }
}
// adds steady current to soma (hyperpolarizing)
// $1 is the current in nA, "-" for hyperpolarizing, "+" for depolarizing
proc setcurrentbias(){ local i, area_soma localobj cell_
 cell_ = new pyramidal() //create a generic cell
 cell_.soma { area_soma = PI*diam*L*1e-8 } // unts converted [mcm2->cm2], area_soma is the area of a soma membrane
 for i = 0,cells.count-1{
   cells.object(i).soma {
      insert bias
	  amp_bias = -$1*1e-6/area_soma //note conversion [nA->mA] by 1e-6 and change of sign
    }
  }
}

// create cells
mkcells(ncells)
// set their positions
setpositions(1000, 0)
// set a steady hyperpolarizing current in soma, -0.1 nA
setcurrentbias(-0.1)

gap=new gapjunction(cells.object(0),axonal_section1,cells.object(1),axonal_section2,gj_conductance,section1_pos, section2_pos)

objectvar pulse
cells.object(0).soma pulse = new Ipulse1(0.5)
pulse.amp=1
pulse.del=5
pulse.num=1
pulse.ton = pulse.toff = 1

access cells.object(0).soma
xopen("2cellsGUI.ses")

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