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TITLE Cardiac second inward current
COMMENT
modified From DiFrancesco & Noble 1985 Phil Trans R Soc Lond 307:353-398
modified for Neuron by FE GANNIER
francois.gannier@univ-tours.fr (University of TOURS)
ENDCOMMENT
INCLUDE "Unit.inc"
INCLUDE "Volume.inc"
NEURON {
SUFFIX Isi
USEION ca READ cao, cai WRITE ica
USEION k READ ko, ki WRITE ik
USEION na READ nao, nai WRITE ina
RANGE P, ica, ik, ina, isi
GLOBAL minf, mtau, hinf, htau
}
PARAMETER {
P = 15 (nA/mM)
alpha_f2 = 5 (/s)
Kmf2 = 0.001 (mM)
}
STATE { : d, f, f2
m n h
}
ASSIGNED {
v (mV)
celsius (degC) : 37
isi (mA/cm2)
ica (mA/cm2)
ik (mA/cm2)
ina (mA/cm2)
eca (mV)
minf ninf hinf
mtau (ms)
ntau (ms)
htau (ms)
cai (mM)
cao (mM)
nai (mM)
nao (mM)
ki (mM)
ko (mM)
beta_f2 (/s)
}
LOCAL RT
INITIAL {
RT = (1000)*R*(273.15+celsius)
rate(v)
m = minf
n = ninf
h = hinf
}
BREAKPOINT { LOCAL com, com2, Eo, icat, inat, ikt
SOLVE states METHOD derivimplicit
Eo = v - 50
com = (1e-06)* P/S*Eo*F/RT * m*n*h
icat = 4*com /(1 - exp(-2*Eo*F/RT))*(cai*exp(100(mV)*F/RT) - cao*exp(-2*F*Eo/RT))
ica = icat
com2 = 0.01*com /(1 - exp(-Eo*F/RT))
ikt = com2*(ki*exp(50(mV)*F/RT) - ko*exp(-F*Eo/RT))
ik = ikt
inat = com2*(nai*exp(50(mV)*F/RT) - nao*exp(-F*Eo/RT))
ina = inat
isi = inat + ikt + icat
}
DERIVATIVE states { : d, f, f2
rate(v)
m' = (minf - m)/mtau
n' = (ninf - n)/ntau
h' = (0.001)*(alpha_f2 - h * (alpha_f2 + beta_f2))
beta_f2 = cai * alpha_f2 / Kmf2
}
FUNCTION alp(v(mV), i) (/ms) { : order d, f
LOCAL Eo, E1
if (i==0) {
Eo = v + 24
if (fabs(Eo*1(/mV)) < 1e-5)
{
alp = (0.001)*120 (/s)
}
else
{
alp = (0.001)*30(/s/mV)*Eo / (1 - exp(-Eo/4(mV)))
}
} else if (i==1) {
E1 = v + 34
if (fabs(E1*1(/mV)) < 1e-5)
{
alp = (0.001)*25 (/s)
}
else
{
alp = (0.001)*6.25(/mV/s)*E1/(exp(E1/4(mV))-1)
}
}
}
FUNCTION bet(v(mV), i) (/ms) { : order d,f
LOCAL Eo
if (i==0) {
Eo = v + 24
if (fabs(Eo*1(/mV)) < 1e-5)
{
bet = (0.001)*120 (/s)
}
else
{
bet = (0.001)*12(/mV/s) *Eo / (exp(Eo/10(mV)) -1)
}
} else if (i==1) {
bet = (0.001)*50(/s)/(1 + exp(-(v + 34)/4(mV)))
}
}
PROCEDURE rate(v (mV)) { LOCAL a,b :
TABLE minf, mtau, ninf, ntau FROM -100 TO 100 WITH 200
a = alp(v,0) b = bet(v,0)
mtau = 1/(a + b)
minf = a * mtau
a = alp(v,1) b = bet(v,1)
ntau = 1/(a + b)
ninf = a * ntau
}
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