Na+ channel dependence of AP initiation in cortical pyramidal neuron (Kole et al. 2008)

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Accession:114394
In this simulation action potential initiation, action potential properties and the role of axon initial segment Na+ channels are investigated in a realistic model of a layer 5 pyramidal neuron axon initial segment. The main Na+ channel properties were constrained by experimental data and the axon initial segment was reconstructed. Model parameters were constrained by direct recordings at the axon initial segment.
Reference:
1 . Kole MH, Ilschner SU, Kampa BM, Williams SR, Ruben PC, Stuart GJ (2008) Action potential generation requires a high sodium channel density in the axon initial segment. Nat Neurosci 11:178-86 [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:
Cell Type(s): Neocortex V1 pyramidal corticothalamic L6 cell;
Channel(s): I Na,t; I K; I M; I h;
Gap Junctions:
Receptor(s):
Gene(s): HCN1; HCN2;
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Active Dendrites; Axonal Action Potentials; Action Potentials;
Implementer(s): Kole, Maarten [m.kole at nin.knaw.nl];
Search NeuronDB for information about:  Neocortex V1 pyramidal corticothalamic L6 cell; I Na,t; I K; I M; I h;
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NN_kole
readme.html
h.mod
Km.mod *
kv.mod *
Kv1.mod
na.mod *
nax.mod *
A3+AIS_original.hoc
figure6a.hoc
initiate_neuron.hoc
mosinit.hoc
panels.ses
screenshot.jpg
screenshot_adjust.jpg
screenshot_morphology.jpg
                            
TITLE Voltage-gated low threshold potassium current from Kv1 subunits

COMMENT

NEURON implementation of a potassium channel from Kv1.1 subunits
Kinetical scheme: Hodgkin-Huxley m^4, no inactivation

Kinetic data taken from: Zerr et al., J.Neurosci. 18 (1998) 2842
Vhalf = -28.8 +/- 2.3 mV; k = 8.1 +/- 0.9 mV

The voltage dependency of the rate constants was approximated by:

alpha = ca * exp(-(v+cva)/cka)
beta = cb * exp(-(v+cvb)/ckb)

Parameters ca, cva, cka, cb, cvb, ckb
are defined in the CONSTANT block.

Laboratory for Neuronal Circuit Dynamics
RIKEN Brain Science Institute, Wako City, Japan
http://www.neurodynamics.brain.riken.jp

Reference: Akemann and Knoepfel, J.Neurosci. 26 (2006) 4602
Date of Implementation: April 2005
Contact: akemann@brain.riken.jp

ENDCOMMENT


NEURON {
	SUFFIX Kv1
	USEION k READ ek WRITE ik
	RANGE gk, gbar, ik
	GLOBAL ninf, taun
}

UNITS {
	(mV) = (millivolt)
	(mA) = (milliamp)
	(nA) = (nanoamp)
	(pA) = (picoamp)
	(S)  = (siemens)
	(nS) = (nanosiemens)
	(pS) = (picosiemens)
	(um) = (micron)
	(molar) = (1/liter)
	(mM) = (millimolar)		
}

CONSTANT {
	q10 = 3

	ca = 0.10 (1/ms) : 0.12889 as original
	cva = 50 (mV)
	cka = -33.90877 (mV)

	cb = 0.12889 (1/ms)
     cvb = 50 (mV)
	ckb = 7.42101 (mV)         
}

PARAMETER {
	v (mV)
	celsius (degC)
	
	gbar = 0.011 (mho/cm2)   <0,1e9>
}


ASSIGNED {
 	ik (mA/cm2) 
	ek (mV)
	gk  (mho/cm2)
	ninf
	taun (ms)
	alphan (1/ms)
	betan (1/ms)
	qt
}

STATE { n }

INITIAL {
	qt = q10^((celsius-22 (degC))/10 (degC))
	rates(v)
	n = ninf
}

BREAKPOINT {
	SOLVE states METHOD cnexp
      gk = gbar * n^4 
	ik = gk * (v - ek)
}

DERIVATIVE states {
	rates(v)
	n' = (ninf-n)/taun 
}

PROCEDURE rates(v (mV)) {
	alphan = alphanfkt(v)
	betan = betanfkt(v)
	ninf = alphan/(alphan+betan) 
	taun = 1/(qt*(alphan + betan))       
}

FUNCTION alphanfkt(v (mV)) (1/ms) {
	alphanfkt = ca * exp(-(v+cva)/cka) 
}

FUNCTION betanfkt(v (mV)) (1/ms) {
	betanfkt = cb * exp(-(v+cvb)/ckb)
}

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