TITLE Mouse sodium current

COMMENT

Kinetics of Carter et al. (2012)

Based on 37 degC recordings from mouse hippocampal CA1 pyramids

Implemented and added Q10 temperature dependence (2.3) by Nathan Gouwens (personal communication)

Modified by Ching-Lung Hsu to revert the correction of liquid junction potential used in Carter et al. (2012)

ENDCOMMENT

NEURON {

	SUFFIX NaV2

	USEION na READ ena WRITE ina

	RANGE g, gbar

}



UNITS {

	(mV) = (millivolt)

	(S) = (siemens)

}



PARAMETER {

	gbar = .015			(S/cm2)



	: kinetic parameters

	Con = 0.01			(/ms)					: closed -> inactivated transitions

	Coff = 2			(/ms)					: inactivated -> closed transitions

	Oon = 8				(/ms)					: open -> Ineg transition

	Ooff = 0.05			(/ms)					: Ineg -> open transition

	alpha = 550			(/ms)

	beta = 12			(/ms)

	gamma = 250			(/ms)					: opening

	delta = 60			(/ms)					: closing



	alfac = 2.51

	btfac = 5.32



	: revert the correction for liquid junction potential
	: x1 = 21, x2 = -21 shift the I-V relationship rightward by ~8 mV
	: (ps. as Nathan pointed out, an error of alpha = 250 in an earlier version of Carter et al. resulted in
	:  a shift of the relationship rightward by ~10 mV, which has been corrected)

	x1 = 21:24			(mV)						: Vdep of activation (alpha)

	x2 = -21:-24			(mV)						: Vdep of deactivation (beta)

}



ASSIGNED {



	: rates

	f01  		(/ms)

	f02  		(/ms)

	f03 		(/ms)

	f04			(/ms)

	f0O 		(/ms)

	f11 		(/ms)

	f12 		(/ms)

	f13 		(/ms)

	f14 		(/ms)

	f1n 		(/ms)

	fi1 		(/ms)

	fi2 		(/ms)

	fi3 		(/ms)

	fi4 		(/ms)

	fi5 		(/ms)

	fin 		(/ms)



	b01 		(/ms)

	b02 		(/ms)

	b03 		(/ms)

	b04			(/ms)

	b0O 		(/ms)

	b11  		(/ms)

	b12 		(/ms)

	b13 		(/ms)

	b14 		(/ms)

	b1n 		(/ms)

	bi1 		(/ms)

	bi2 		(/ms)

	bi3 		(/ms)

	bi4 		(/ms)

	bi5 		(/ms)

	bin 		(/ms)



	v			(mV)

 	ena			(mV)

	ina			(milliamp/cm2)

	g			(S/cm2)

	celsius		(degC)

}



STATE {

	C1 FROM 0 TO 1

	C2 FROM 0 TO 1

	C3 FROM 0 TO 1

	C4 FROM 0 TO 1

	C5 FROM 0 TO 1

	I1 FROM 0 TO 1

	I2 FROM 0 TO 1

	I3 FROM 0 TO 1

	I4 FROM 0 TO 1

	I5 FROM 0 TO 1

	O FROM 0 TO 1

	I6 FROM 0 TO 1

}



BREAKPOINT {

	SOLVE activation METHOD sparse

	g = gbar * O

	ina = g * (v - ena)

}



INITIAL {

 rates(v)

 SOLVE seqinitial

}



KINETIC activation

{

	rates(v)

	~ C1 <-> C2					(f01,b01)

	~ C2 <-> C3					(f02,b02)

	~ C3 <-> C4					(f03,b03)

	~ C4 <-> C5					(f04,b04)

	~ C5 <-> O					(f0O,b0O)

	~ O <-> I6					(fin,bin)

	~ I1 <-> I2					(f11,b11)

	~ I2 <-> I3					(f12,b12)

	~ I3 <-> I4					(f13,b13)

	~ I4 <-> I5					(f14,b14)

	~ I5 <-> I6					(f1n,b1n)

	~ C1 <-> I1					(fi1,bi1)

	~ C2 <-> I2					(fi2,bi2)

	~ C3 <-> I3					(fi3,bi3)

 	~ C4 <-> I4					(fi4,bi4)

 	~ C5 <-> I5					(fi5,bi5)



	CONSERVE C1 + C2 + C3 + C4 + C5 + O + I1 + I2 + I3 + I4 + I5 + I6 = 1

}



LINEAR seqinitial { : sets initial equilibrium

	~          I1*bi1 + C2*b01 - C1*(    fi1+f01) = 0

	~ C1*f01 + I2*bi2 + C3*b02 - C2*(b01+fi2+f02) = 0

	~ C2*f02 + I3*bi3 + C4*b03 - C3*(b02+fi3+f03) = 0

	~ C3*f03 + I4*bi4 + C5*b04 - C4*(b03+fi4+f04) = 0

	~ C4*f04 + I5*bi5 + O*b0O  - C5*(b04+fi5+f0O) = 0

	~ C5*f0O + I6*bin          - O*(b0O+fin)      = 0



	~          C1*fi1 + I2*b11 - I1*(    bi1+f11) = 0

	~ I1*f11 + C2*fi2 + I3*b12 - I2*(b11+bi2+f12) = 0

	~ I2*f12 + C3*fi3 + I4*bi3 - I3*(b12+bi3+f13) = 0

	~ I3*f13 + C4*fi4 + I5*b14 - I4*(b13+bi4+f14) = 0

	~ I4*f14 + C5*fi5 + I6*b1n - I5*(b14+bi5+f1n) = 0



	~ C1 + C2 + C3 + C4 + C5 + O + I1 + I2 + I3 + I4 + I5 + I6 = 1

}



PROCEDURE rates(v(mV) )

{

	LOCAL qt

	qt = 2.3^((celsius-37)/10)



	f01 = qt * 4 * alpha * exp(v/x1)

	f02 = qt * 3 * alpha * exp(v/x1)

	f03 = qt * 2 * alpha * exp(v/x1)

	f04 = qt * 1 * alpha * exp(v/x1)

	f0O = qt * gamma

	f11 = qt * 4 * alpha * alfac * exp(v/x1)

	f12 = qt * 3 * alpha * alfac * exp(v/x1)

	f13 = qt * 2 * alpha * alfac * exp(v/x1)

	f14 = qt * 1 * alpha * alfac * exp(v/x1)

	f1n = qt * gamma

	fi1 = qt * Con

	fi2 = qt * Con * alfac

	fi3 = qt * Con * alfac^2

	fi4 = qt * Con * alfac^3

	fi5 = qt * Con * alfac^4

	fin = qt * Oon



	b01 = qt * 1 * beta * exp(v/x2)

	b02 = qt * 2 * beta * exp(v/x2)

	b03 = qt * 3 * beta * exp(v/x2)

	b04 = qt * 4 * beta * exp(v/x2)

	b0O = qt * delta

	b11 = qt * 1 * beta * exp(v/x2) / btfac

	b12 = qt * 2 * beta * exp(v/x2) / btfac

	b13 = qt * 3 * beta * exp(v/x2) / btfac

	b14 = qt * 4 * beta * exp(v/x2) / btfac

	b1n = qt * delta

	bi1 = qt * Coff

	bi2 = qt * Coff / (btfac)

	bi3 = qt * Coff / (btfac^2)

	bi4 = qt * Coff / (btfac^3)

	bi5 = qt * Coff / (btfac^4)

	bin = qt * Ooff

}