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;
: NA1_GP.MOD
:
:				      	   b  -  isb01-isb02-isb03-isb04-isb05-...-isb10
:				  		   |
: c1 - c2 - c3 - c4 - c5 - o  - iso01-iso02-iso03-iso04-iso05-...-iso10
: |    |    |    |    |    |
: i1 - i2 - i3 - i4 - i5 - i6 - isi01-isi02-isi03-isi04-isi05-...-isi10
:
: 09.06.2005
:
: Globus pallidus Nav1.1+1.2 channel

NEURON {
	SUFFIX na1_gp
	USEION na READ ena WRITE ina
	RANGE g, ina, gbar, m, bo, ob,Cn,Cf
	GLOBAL Con, Coff, n
	GLOBAL Oon0, hOon, cOon
	GLOBAL Ooff0, hOoff, cOoff
	GLOBAL a0, vha, vca
	GLOBAL b0, vhb, vcb
	GLOBAL g0
	GLOBAL d0
	GLOBAL aSo, aSi, aSb, bS, bS1, k
	GLOBAL SoR, SoH, SoC
	GLOBAL SiR, SiH, SiC
	GLOBAL SbR, SbH, SbC
	GLOBAL ob0, bl0, bslope, bvh
}

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

PARAMETER {
	gbar = 1	(S/cm2)

	a0 = 9		(1/ms)	: alpha
	vha  = -18	(mV)
	vca = 15	(mV)

	b0 = 5		(1/ms)	: beta
	vhb = -58	(mV)
	vcb = -60	(mV)

	g0 = 40		(1/ms)	: gamma

	d0 = 25		(1/ms)	: delta

	SoR = 0.0018	(1/ms)
	SoH	 = -25
	SoC  = 100

	SiR = 0.00023	(1/ms)
	SiH	 = -25
	SiC  = 100

	SbR = 0.00023	(1/ms)
	SbH	 = -25
	SbC  = 100

	bS1  = 0.0005	(1/ms)

	aSo = 3.3e-05	(1/ms)
	aSi = 3.3e-05	(1/ms)
	aSb = 3.3e-05	(1/ms)
	bS  = 4.4e-05		(1/ms)
	k = 4.0366


	Con = 0.025	(1/ms)
	Coff = 0.005	(1/ms)
	n = 2

	Oon0 = 3	(1/ms)
	hOon = -20	(mV)
	cOon = 30	(mV)

	Ooff0 = 0.001	(1/ms)
	hOoff = -20	(mV)
	cOoff = -50	(mV)

	ob0 = 1	(1/ms)	: "forward block rate"
	bl0 = 0.08	(1/ms)	: "reverse block rate"
	bslope = 25	(mV)	: "slope factor for block"
	bvh = 0		(mV)	: "half block voltage"

	Cq10 = 4
	celsius		(degC)
}

ASSIGNED {
	v	(mV)
	ena 	(mV)
	g	(S/cm2)
	ina	(mA/cm2)
	alpha  	(1/ms)
	beta	(1/ms)
	gamma   (1/ms)
	delta	(1/ms)
	Oon	(1/ms)
	Ooff	(1/ms)
	m
	ob	(1/ms)
	bo	(1/ms)
	Cn	(1/ms)
	Cf	(1/ms)
	q10
	aSo1
	aSi1
	aSb1
}

STATE {
	c1		: closed
	c2
	c3
	c4
	c5
	ct		: total closed
	o		: open
	i1		: fast inactivated
	i2
	i3
	i4
	i5
	i6
	ift		: total fast inactivated
	iso01	: slow inact from o
	iso02
	iso03
	iso04
	iso05
	iso06
	iso07
	iso08
	iso09
	iso10
	isot	: total slow inact from o
	isb01	: slow inact from b
	isb02
	isb03
	isb04
	isb05
	isb06
	isb07
	isb08
	isb09
	isb10
	isbt 	: total slow inact from b
	isi01	: slow inact from i6
	isi02
	isi03
	isi04
	isi05
	isi06
	isi07
	isi08
	isi09
	isi10
	isit 	: total slow inact from i6
	ist		: total slow inactivated
	it		: total inactivated
	bl		: (open) block
	avail	: fraction available
}

BREAKPOINT {
	SOLVE kin METHOD sparse
	g = gbar*o
	ina = g*(v-ena)
	ct = c1 + c2 + c3 + c4 + c5
	ift = i1 + i2 + i3 + i4 + i5 + i6
	isot = iso01 + iso02 + iso03 + iso04 + iso05 + iso06 + iso07 + iso08 + iso09 + iso10
	isit = isi01 + isi02 + isi03 + isi04 + isi05 + isi06 + isi07 + isi08 + isi09 + isi10
	isbt = isb01 + isb02 + isb03 + isb04 + isb05 + isb06 + isb07 + isb08 + isb09 + isb10
	ist = isot + isit + isbt
	it = ift + ist
	avail = o + ct
}

INITIAL {
	SOLVE kin STEADYSTATE sparse
}

KINETIC kin{
	rates(v)

	~ c1 <-> c2	(4*alpha, beta)
	~ c2 <-> c3	(3*alpha, 2*beta)
	~ c3 <-> c4	(2*alpha, 3*beta)
	~ c4 <-> c5	(alpha, 4*beta)
	~ c5 <-> o	(gamma, delta)
	~ o <-> iso01	(q10*aSo1, q10*bS1)
	~ iso01 <-> iso02	(q10*aSo*k, q10*bS*k)
	~ iso02 <-> iso03	(q10*aSo*k^2, q10*bS*k^2)
	~ iso03 <-> iso04	(q10*aSo*k^3, q10*bS*k^3)
	~ iso04 <-> iso05	(q10*aSo*k^4, q10*bS*k^4)
	~ iso05 <-> iso06	(q10*aSo*k^5, q10*bS*k^5)
	~ iso06 <-> iso07	(q10*aSo*k^6, q10*bS*k^6)
	~ iso07 <-> iso08	(q10*aSo*k^7, q10*bS*k^7)
	~ iso08 <-> iso09	(q10*aSo*k^8, q10*bS*k^8)
	~ iso09 <-> iso10	(q10*aSo*k^9, q10*bS*k^9)

	~ i1 <-> i2	(4*alpha*n, beta/n)
	~ i2 <-> i3	(3*alpha*n, 2*beta/n)
	~ i3 <-> i4	(2*alpha*n, 3*beta/n)
	~ i4 <-> i5	(alpha*n, 4*beta/n)
	~ i5 <-> i6	(gamma*m, delta/m)
	~ i6 <-> isi01	(q10*aSi1, q10*bS1)
	~ isi01 <-> isi02	(q10*aSi*k, q10*bS*k)
	~ isi02 <-> isi03	(q10*aSi*k^2, q10*bS*k^2)
	~ isi03 <-> isi04	(q10*aSi*k^3, q10*bS*k^3)
	~ isi04 <-> isi05	(q10*aSi*k^4, q10*bS*k^4)
	~ isi05 <-> isi06	(q10*aSi*k^5, q10*bS*k^5)
	~ isi06 <-> isi07	(q10*aSi*k^6, q10*bS*k^6)
	~ isi07 <-> isi08	(q10*aSi*k^7, q10*bS*k^7)
	~ isi08 <-> isi09	(q10*aSi*k^8, q10*bS*k^8)
	~ isi09 <-> isi10	(q10*aSi*k^9, q10*bS*k^9)

	~ c1 <-> i1	(Cn/n^4, Cf*n^4)
	~ c2 <-> i2	(Cn/n^3, Cf*n^3)
	~ c3 <-> i3	(Cn/n^2, Cf*n^2)
	~ c4 <-> i4	(Cn/n, Cf*n)
	~ c5 <-> i5	(Cn, Cf)
	~ o <-> i6	(Oon, Ooff)

	~ o <-> bl	(ob,bo)
	~ bl <-> isb01	(q10*aSb1, q10*bS1)
	~ isb01 <-> isb02	(q10*aSb*k, q10*bS*k)
	~ isb02 <-> isb03	(q10*aSb*k^2, q10*bS*k^2)
	~ isb03 <-> isb04	(q10*aSb*k^3, q10*bS*k^3)
	~ isb04 <-> isb05	(q10*aSb*k^4, q10*bS*k^4)
	~ isb05 <-> isb06	(q10*aSb*k^5, q10*bS*k^5)
	~ isb06 <-> isb07	(q10*aSb*k^6, q10*bS*k^6)
	~ isb07 <-> isb08	(q10*aSb*k^7, q10*bS*k^7)
	~ isb08 <-> isb09	(q10*aSb*k^8, q10*bS*k^8)
	~ isb09 <-> isb10	(q10*aSb*k^9, q10*bS*k^9)

	CONSERVE c1+c2+c3+c4+c5+i1+i2+i3+i4+i5+i6+iso01+iso02+iso03+iso04+iso05+iso06+iso07+iso08+iso09+iso10+isi01+isi02+isi03+isi04+isi05+isi06+isi07+isi08+isi09+isi10+isb01+isb02+isb03+isb04+isb05+isb06+isb07+isb08+isb09+isb10+o+bl=1

}

PROCEDURE rates(v(mV)) {
	q10 = Cq10^((celsius-23 (degC))/10 (degC))

	alpha = q10*a0*exp((v-vha)/vca)
	beta = q10*b0*exp((v-vhb)/vcb)
	gamma = q10*g0
	delta = q10*d0

	ob = q10*ob0
	bo = q10*bl0*exp(-(v-bvh)/bslope)

	Cn=q10*Con
	Cf=q10*Coff

	Oon = q10*Oon0*exp((v-hOon)/cOon)
	Ooff = q10*Ooff0*exp((v-hOoff)/cOoff)

	m = ((Oon/Ooff)/(Con/Coff))^(1/2)

	aSo1 = q10*SoR*exp((v-SoH)/SoC)
	aSi1 = q10*SiR*exp((v-SiH)/SiC)
	aSb1 = q10*SbR*exp((v-SbH)/SbC)
}

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