Explaining pathological changes in axonal excitability by dynamical analysis (Coggan et al. 2011)

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Accession:143072
"... To help decipher the biophysical basis for ‘paroxysmal’ spiking, we replicated afterdischarge (i.e. continued spiking after a brief stimulus) in a minimal conductance-based axon model. ... A perturbation could abruptly switch the system between two (quasi-)stable attractor states: rest and repetitive spiking. ... Initiation of afterdischarge was explained by activation of the persistent inward current forcing the system to cross a saddle point that separates the basins of attraction associated with each attractor. Termination of afterdischarge was explained by the attractor associated with repetitive spiking being destroyed. ... The model also explains other features of paroxysmal symptoms, including temporal summation and refractoriness."
Reference:
1 . Coggan JS, Ocker GK, Sejnowski TJ, Prescott SA (2011) Explaining pathological changes in axonal excitability through dynamical analysis of conductance-based models. J Neural Eng 8:065002 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Axon;
Brain Region(s)/Organism:
Cell Type(s):
Channel(s):
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: XPP;
Model Concept(s): Nociception;
Implementer(s): Prescott, Steven [steve.prescott at sickkids.ca]];

// myelinated axon with soma (Jay Coggan)
 
//***********************************************************************
 

naxonseg = 80
create node[naxonseg],myelin[naxonseg]
create soma
create hill
create iseg

soma {
	nseg = 3
	L = 15	 
	diam = 15		
	

	
	insert nax
	insert HT
	gnabar_nax = 0.08	
	gl_nax = 0.003		
	gbar_HT = .79		
	gnapbar_nax = 0.0003	
	
	insert kaccum2
	insert naaccum2
	insert nadifus
	insert kdifus
	
	
}


 hill { 		
    L = 8
    nseg = 4
    diam(0:1) = 4:1    

	insert nax
	insert HT
	gnabar_nax = 0.08	
	gl_nax = 0.003	
	gbar_HT = 0.79 	
	gnapbar_nax = 0.0002	
	
	

	insert kaccum2
	insert naaccum2
	insert nadifus
	insert kdifus
	
	
 }


  iseg {			
     L = 10
     nseg = 5
     diam = 1				


	insert nax
	insert HT
	gnabar_nax = 0.08		
	gl_nax = 0.003				
	gbar_HT = 0.79 			
	gnapbar_nax = 0.0002	

	

	insert kaccum2
	insert naaccum2
	insert nadifus
	insert kdifus
	
	
 }


proc createAxon() {


create myelin[naxonseg],node[naxonseg]

  for i=0,naxonseg-1 {
    myelin[i] {         
     nseg = 20 
      L = 200							 
      diam = 1						         
    }
}
    for i=0,naxonseg-1{
 node[i] {          
      nseg = 1 
      L = 1					         
      diam = 1					
 	} 
}   

// connections

//connect soma(1), myelin[0](0)


connect soma(1), hill(0)		
connect hill(1), iseg(0)
connect iseg(1), myelin[0](0)


  for i=0,naxonseg-1  {   
    
    
    connect node[i](0), myelin[i](1)
    
  }

  for i=0,naxonseg-2  { 
   connect myelin[i+1](0), node[i](1)
	}
}


//************************************************************************

proc setRacm() {

for i=0,naxonseg-1{
 	node[i] {      
    		nseg = 1	
     		cm = 2.0		

		} 
	}   
		
	
 for i=0,naxonseg-1 {
    	myelin[i] {  
       
    		cm = 0.05    
 	  
 		
			insert kaccum2
			insert naaccum2
			insert nadifus
			insert kdifus
 		}
	}

	soma	{
		cm = 2.0

	}


iseg	{
		cm = 2.0

	}

hill	{
		cm = 2.0

	}


	forall {
		Ra = 150.0	
		
	}
}

proc addchannels() {


	for ii = 0, naxonseg-1 {
		node[ii] {
			


			insert nax
			insert HT
			gnabar_nax = 1.5
			gl_nax = 0.07		
			gbar_HT = 1.6		
			gnapbar_nax = 0.0019
			
			

			insert kaccum2
			insert naaccum2
			insert nadifus
			insert kdifus
			
			
		}
	}
}


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