Multicompartmental cerebellar granule cell model (Diwakar et al. 2009)

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Accession:116835
A detailed multicompartmental model was used to study neuronal electroresponsiveness of cerebellar granule cells in rats. Here we show that, in cerebellar granule cells, Na+ channels are enriched in the axon, especially in the hillock, but almost absent from soma and dendrites. Numerical simulations indicated that granule cells have a compact electrotonic structure allowing EPSPs to diffuse with little attenuation from dendrites to axon. The spike arose almost simultaneously along the whole axonal ascending branch and invaded the hillock, whose activation promoted spike back-propagation with marginal delay (<200 micros) and attenuation (<20 mV) into the somato-dendritic compartment. For details check the cited article.
Reference:
1 . Diwakar S, Magistretti J, Goldfarb M, Naldi G, D'Angelo E (2009) Axonal Na+ channels ensure fast spike activation and back-propagation in cerebellar granule cells J Neurophysiol 101(2):519-32 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Neuron or other electrically excitable cell;
Brain Region(s)/Organism: Cerebellum;
Cell Type(s): Cerebellum interneuron granule cell;
Channel(s): I A; I M; I h; I K,Ca; I Sodium; I Calcium; I Potassium; I A, slow;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Active Dendrites; Detailed Neuronal Models; Axonal Action Potentials; Action Potentials; Intrinsic plasticity;
Implementer(s): Diwakar, Shyam [shyam at amrita.edu];
Search NeuronDB for information about:  Cerebellum interneuron granule cell; I A; I M; I h; I K,Ca; I Sodium; I Calcium; I Potassium; I A, slow;
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GrC
fig10
readme.html
AmpaCOD.mod *
GRC_CA.mod *
GRC_CALC.mod *
GRC_GABA.mod *
GRC_KA.mod *
GRC_KCA.mod *
GRC_KIR.mod *
GRC_KM.mod *
GRC_KV.mod *
GRC_LKG1.mod *
GRC_LKG2.mod *
GRC_NA.mod *
NmdaS.mod *
Pregen.mod *
ComPanel.hoc
Grc_Cell.hoc
mosinit.hoc
Parametri.hoc
screenshot.jpg
simple.ses
Start.hoc
                            
TITLE AMPACOD  

COMMENT
	AMPA model from Paper (version 15 sept 2004).
	
ENDCOMMENT

NEURON {
	POINT_PROCESS AmpaCOD	
	NONSPECIFIC_CURRENT i	
	RANGE r1FIX,r2,r3,r4,r5,r1,r6,r6FIX
	RANGE g,gmax,kB,Cdur,Erev 
	RANGE gg1,gg2,gg3,Tdiff
	RANGE T,Tmax,Trelease 	
	RANGE tau_1,tau_rec,tau_facil,U,u0	
	RANGE A1,A2,A3,tau_dec1,tau_dec2,tau_dec3		: comes from fit 
	RANGE tdelay,ton	 
}

UNITS {
	(nA) = (nanoamp)
	(mV) = (millivolt)	
	(mM) = (milli/liter)
	(pS) = (picosiemens)
	(nS) = (nanosiemens)
	(um) = (micrometer)
	PI   = (pi)(1)
}

PARAMETER {
	: Parametri Postsinaptici
	r1FIX		= 5.4		(/ms/mM) 	 
	r2		= 0.82		(/ms)		 
	r3		= 0		(/ms)		 
	r4		= 0		(/ms)		 
	r5		= 0.013		(/ms)		
	r6FIX		= 1.12		(/ms/mM)	
	gmax		= 700 		(nS)		 
	Cdur		= 0.3		(ms)		 
	Erev		= 0		(mV)
	kB		= 0.44		(mM)
		
	: Diffusion: M=21500, R=1.033, D=0.223, lamd=0.02			
	A1 			= 0.131837 
	A2			= 0.0555027	 
	A3 			= 0.0135232	 
	tau_dec1 		= 3.4958	 
	tau_dec2 		= 16.6317	 
	tau_dec3 		= 128.983	

	: Parametri Presinaptici
	tau_1 		= 3 (ms) 	< 1e-9, 1e9 >
	tau_rec 	= 35.1 (ms) 	< 1e-9, 1e9 > 	
	tau_facil 	= 10.8 (ms) 	< 0, 1e9 > 	

	U 		= 0.416 (1) 	< 0, 1 >
	u0 		= 0 (1) 	< 0, 1 >	: se u0=0 al primo colpo y=U
	Tmax		= 1  (mM)
}


ASSIGNED {
	v		(mV)		: postsynaptic voltage
	i 		(nA)		: current = g*(v - Erev)
	g 		(pS)		: conductance
	r1		(/ms)
	r6		(/ms)
	T		(mM)
	Trelease	(mM)
	Tdiff		(mM)
	tdelay		(ms)
	Tdiff_0		(mM)
	ton		(ms)	
	
	x
	PRE
}

STATE {	
	C
	O
	D
	gg1
	gg2
	gg3
	sink
}	
	

INITIAL {
	C		=	1
	O		=	0
	D		=	0
	T		=	0 	(mM)
	Tdiff		=	0	(mM)
	Trelease	=	0 	(mM)
	Tdiff_0		=	0	(mM)
	gg1		=	0
	gg2		=	0
	gg3		=	0   
	ton		=  	-1   (ms)
	PRE		=	0
}

FUNCTION SET_tdelay(R,D){ tdelay=0.25*R*R/D } 

BREAKPOINT {
	if( (t-ton)>tdelay  ){
		Tdiff=gg1+gg2+gg3
		Tdiff_0 = Tdiff
	}else{
		Tdiff=Tdiff_0+(A1+A2+A3)*PRE*(t-ton)/tdelay
	}
	Trelease=T+Tdiff
	SOLVE kstates METHOD sparse
	g =gmax * O
	i = (1e-6) * g * (v - Erev) 
}


KINETIC kstates {
	: Postsynaptic scheme
	r1 = r1FIX * Trelease^2 / (Trelease + kB)^2
	r6 = r6FIX * Trelease^2 / (Trelease + kB)^2
	~ C  <-> O	(r1,r2)
	~ O  <-> D	(r3,r4)
	~ D  <-> C	(r5,r6)
	CONSERVE C+O+D = 1
	: Glutamate diffusion wave
	~ gg1 <-> sink (1/tau_dec1,0)
	~ gg2 <-> sink (1/tau_dec2,0)
	~ gg3 <-> sink (1/tau_dec3,0)
}


NET_RECEIVE(weight, on, nspike, flagtdel,t0 (ms),y, z, u, tsyn (ms)) {
	INITIAL {
		flagtdel=1
		nspike = 1
		Tdiff=0
		y=0
		z=0
		u=u0
		tsyn=t
	}
   	if (flag == 0) { 
		nspike = nspike + 1
		if (!on) {
			ton=t
			t0=t
			on=1				
			z=z*exp(-(t-tsyn)/tau_rec)
			z=z+(y*(exp(-(t - tsyn)/tau_1)-exp(-(t-tsyn)/tau_rec))/(tau_1/tau_rec-1))
			y=y*exp(-(t-tsyn)/tau_1)			
			x=1-y-z
			if(tau_facil>0){ 
				u=u*exp(-(t-tsyn)/tau_facil)
				u=u+U*(1-u)							
			}else{u=U}
			y=y+x*u
			PRE=y
			T=Tmax*y
			tsyn=t						
		}
		net_send(Cdur,nspike)
		net_send(tdelay,flagtdel)						
    	}
	if(flag==nspike){ 		
		T = 0
		on = 0
	}
	if (flag == flagtdel){
		flagtdel = flagtdel+1
		state_discontinuity(gg1,gg1+A1*x*u)	 
		state_discontinuity(gg2,gg2+A2*x*u)	 
		state_discontinuity(gg3,gg3+A3*x*u)	 
	}
}	 

 

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