Nav1.6 sodium channel model in globus pallidus neurons (Mercer et al. 2007)

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Accession:105385
Model files for the paper Mercer JN, Chan CS, Tkatch T, Held J, Surmeier DJ. Nav1.6 sodium channels are critical to pacemaking and fast spiking in globus pallidus neurons.,J Neurosci. 2007 Dec 5;27(49):13552-66.
Reference:
1 . Mercer JN, Chan CS, Tkatch T, Held J, Surmeier DJ (2007) Nav1.6 sodium channels are critical to pacemaking and fast spiking in globus pallidus neurons. J Neurosci 27:13552-66 [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): Globus pallidus neuron;
Channel(s): I Na,p; I Na,t; I K; I h; I K,Ca; I Sodium; I Calcium; I Potassium;
Gap Junctions:
Receptor(s):
Gene(s): Nav1.6 SCN8A;
Transmitter(s):
Simulation Environment: NEURON;
Model Concept(s): Action Potential Initiation; Action Potentials; Parkinson's;
Implementer(s): Held, Joshua [j-held at northwestern.edu];
Search NeuronDB for information about:  I Na,p; I Na,t; I K; I h; I K,Ca; I Sodium; I Calcium; I Potassium;
: KV4_GP.MOD
:
: c1 - c2 - c3 - c4 - o
: |    |    |    |    |
: i1 - i2 - i3 - i4 - i5 - is

NEURON {
	SUFFIX kv4_gp
	USEION k READ ek WRITE ik
	RANGE g, ik, gbar
	GLOBAL alpha, beta
	GLOBAL ci, ic, oi, io, a, b, am, bm, vc, gamma, delta, vha, vhb
	GLOBAL i5is, isi5
	GLOBAL ratio
	GLOBAL q10i, q10v
}

UNITS {
	(mV)	= (millivolt)
	(S)	= (siemens)
	(mA)	= (milliamp)
}

PARAMETER {
	gbar = 1	(S/cm2)
	gamma = 200	(1/ms)
	delta = 4	(1/ms)
	a = 3
	b = 40
	ic = 500 	(1/ms)
	oi = 1e-9	(1/ms)
	io = .01	(1/ms)
	ci = .2		(1/ms)
	am = 1		(1/ms)
	bm = 7		(1/ms)
	vc = 10		(mV)
	vha = -75	(mV)
	vhb = -30	(mV)
	i5is = .001	(1/ms)
	isi5 = .001	(1/ms)
	q10i = 3
	q10v = 3
	celsius		(degC)
}

ASSIGNED {
	v	(mV)
	ek	(mV)
	g	(S/cm2)
	ik	(mA/cm2)
	alpha	(1/ms)
	beta    (1/ms)
	ratio
}

STATE {
	c1
	c2
	c3
	c4
	o
	i1
	i2
	i3
	i4
	i5
	is
	ift
	it
}

BREAKPOINT {
	SOLVE kin METHOD sparse
	g = gbar*o
	ik = g*(v-ek)
	ift = i1+i2+i3+i4+i5
	it = ift+is
}

INITIAL {
	SOLVE kin STEADYSTATE sparse
}

KINETIC kin{
	LOCAL q10
	q10 = q10i^((celsius - 22 (degC))/10 (degC))
	rates(v)
	~ c1 <-> c2 (3*alpha,beta)
	~ c2 <-> c3 (2*alpha,2*beta)
	~ c3 <-> c4 (alpha,3*beta)
	~ c4 <-> o  (q10*gamma,q10*delta)

	~ i1 <-> i2 (3*alpha*a,beta/b)
	~ i2 <-> i3 (2*alpha*a,2*beta/b)
	~ i3 <-> i4 (alpha*a,3*beta/b)
	~ i4 <-> i5 (q10*gamma,q10*delta)
	~ i5 <-> is (q10*i5is,q10*isi5)

	~ i1 <-> c1 (q10*ic,q10*ci)
	~ i2 <-> c2 (q10*ic/b,q10*ci*a)
	~ i3 <-> c3 (q10*ic/b^2,q10*ci*a^2)
	~ i4 <-> c4 (q10*ic/b^3,q10*ci*a^3)
	~ i5 <-> o  (q10*io,q10*oi)

	CONSERVE c1+c2+c3+c4+i1+i2+i3+i4+i5+o+is=1
}

PROCEDURE rates(v(millivolt)) {LOCAL q10
    q10 = q10v^((celsius - 22 (degC))/10 (degC))
    alpha = q10*am*exp((v-vha)/vc)
    beta = q10*bm*exp((v-vhb)/-vc)
    ratio = (oi*ic/((io*(a^3)*(b^3))))/ci
}

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