Double cable myelinated axon (Layer 5 pyramidal neuron; Cohen et al 2020)

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Accession:260967
The periaxonal space in myelinated axons is conductive (~50 ohm cm). Together with a rapidly charging myelin sheath and relatively sealed paranodes, periaxonal conduction shapes the saltating voltage profiles of transaxonal (Vm), transmyelin (Vmy) and transfibre (Vmym) potentials. This model exemplifies double cable saltatory conduction across both time and space, and is the same cell (#6) as seen in Movie S4 of Cohen et al. 2020. This model version allows one to visualize and manipulate the controlling parameters of a propagating action potential. Further notes: The corresponding potentials in NEURON to those named above are v, vext (or vext[0]) and v+vext, respectively. The loaded biophysical parameters were those optimized for this cell (Cohen et al. 2020).
Reference:
1 . Cohen CCH, Popovic MA, Klooster J, Weil M, Möbius W, Nave K, Kole MHP (2020) Saltatory Conduction along Myelinated Axons Involves a Periaxonal Nanocircuit Cell
Model Information (Click on a link to find other models with that property)
Model Type: Axon; Channel/Receptor; Dendrite; Extracellular; Glia; Neuron or other electrically excitable cell;
Brain Region(s)/Organism:
Cell Type(s): Neocortex L5/6 pyramidal GLU cell; Myelinated neuron;
Channel(s): Ca pump; I Calcium; I h; I K,Ca; I K,leak; I L high threshold; I T low threshold; I M; I Na,p; I Na,t; I Sodium; I Potassium;
Gap Junctions:
Receptor(s):
Gene(s):
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Action Potentials; Active Dendrites; Axonal Action Potentials; Conductance distributions; Conductances estimation; Detailed Neuronal Models; Electrotonus; Extracellular Fields; Membrane Properties; Multiple sclerosis; Parameter sensitivity; Double cable;
Implementer(s): Cohen, Charles CH [c.cohen at gmx.com]; Kole, Maarten [m.kole at nin.knaw.nl];
Search NeuronDB for information about:  Neocortex L5/6 pyramidal GLU cell; I Na,p; I Na,t; I L high threshold; I T low threshold; I K,leak; I M; I h; I K,Ca; I Sodium; I Calcium; I Potassium; Ca pump; 
TITLE Axonal Kv7-current

COMMENT

Model of cortical pyramidal neuron Kv7/M currents. The kinetic parameters, voltage-dependence and reversal potentials are estimated by fitting and analysis of axonal K7/M-currents at 33 degrees celsius. MHP Kole, Canberra, 2008 and Amsterdam, 2011.

Made threadsafe (CCohen)

ENDCOMMENT

UNITS {
	
	(mA) = (milliamp)
	(mV) = (millivolt)
	(pS) = (picosiemens)
	(um) = (micron)
}

INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}

PARAMETER {	
	
	dt	(ms)
	v 	(mV)
	celsius	(degC)
	Ca	=	0.0388
	Cb	= 	0.00168
	za	=	0.90979
	zb	=	1.23645
	gbar	= 	20 	(pS/um2)	: 0.002 mho/cm2
	temp	= 	34	(degC)		: original temp
	q10  	= 	3.0				: temperature sensitivity
}

NEURON {
	
	SUFFIX kv7
	USEION k READ ek WRITE ik
	RANGE gbar, ik
	THREADSAFE
}

STATE { m }

ASSIGNED {
	
	ik (mA/cm2)
	gk (pS/um2)
	ek (mV)
	tadj
}

INITIAL {
	
	m=alpha(v)/(beta(v)+alpha(v))
	tadj = q10^((celsius - temp)/10)
}

BREAKPOINT {
	
	SOLVE state METHOD cnexp
	tadj = q10^((celsius - temp)/10)	:this repeated calculation allows changes in temperature during the simulation
	ik = (1e-4) * gbar * m * (v-ek)
}

FUNCTION alpha(v(mV)) {
	
	alpha = tadj*Ca*exp(za*v*0.037788)
}

FUNCTION beta(v(mV)) {
	
	beta = tadj*Cb*exp(-zb*v*0.037788)
}

DERIVATIVE state {
	
	m' = (1-m)*alpha(v) - m*beta(v)
}

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