COMMENT
NA2_CH.MOD
c1 - c2 - c3 - c4 - c5 - o - is1
| | | | | |
i1 - i2 - i3 - i4 - i5 - i6 - is2
FAST
6/18/2003
ENDCOMMENT
NEURON {
SUFFIX na2_ch
USEION na READ ena WRITE ina
RANGE g, ina, gbar, a
GLOBAL Con, Coff, Oon, Ooff
GLOBAL a0, vha, vca
GLOBAL b0, vhb, vcb
GLOBAL g0
GLOBAL d0
GLOBAL aS1, aS2, bS
}
UNITS {
(mV) = (millivolt)
(mA) = (milliamp)
(S) = (siemens)
}
PARAMETER {
gbar = 1 (S/cm2)
a0 = 37 (1/ms) : alpha
vha = 45 (mV)
vca = 40 (mV)
b0 = 10 (1/ms) : beta
vhb = -50 (mV)
vcb = -10 (mV)
g0 = 40 (1/ms) : gamma
d0 = 30 (1/ms) : delta
aS1 = 0.0025 (1/ms)
aS2 = 0.0002 (1/ms)
bS = 0.00017 (1/ms)
Con = 0.001 (1/ms)
Coff = 0.1 (1/ms)
Oon = 1.6 (1/ms)
Ooff = 0.01 (1/ms)
}
ASSIGNED {
v (mV)
ena (mV)
g (S/cm2)
ina (mA/cm2)
alpha (1/ms)
beta (1/ms)
gamma (1/ms)
delta (1/ms)
a
}
STATE {
c1 : closed
c2
c3
c4
c5
ct : total closed
o : open
i1 : fast inactivated
i2
i3
i4
i5
i6
ift : total fast inactivated
is1 : slow inactivated
is2
ist : total slow inactivated
it : total inactivated
}
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
ist = is1 + is2
it = ift + ist
}
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 <-> is1 (aS1, bS)
~ i1 <-> i2 (4*alpha*a, beta/a)
~ i2 <-> i3 (3*alpha*a, 2*beta/a)
~ i3 <-> i4 (2*alpha*a, 3*beta/a)
~ i4 <-> i5 (alpha*a, 4*beta/a)
~ i5 <-> i6 (gamma, delta)
~ i6 <-> is2 (aS2, bS)
~ c1 <-> i1 (Con, Coff)
~ c2 <-> i2 (Con*a, Coff/a)
~ c3 <-> i3 (Con*a^2, Coff/a^2)
~ c4 <-> i4 (Con*a^3, Coff/a^3)
~ c5 <-> i5 (Con*a^4, Coff/a^4)
~ o <-> i6 (Oon, Ooff)
CONSERVE c1+c2+c3+c4+c5+i1+i2+i3+i4+i5+i6+is1+is2+o=1
}
PROCEDURE rates(v(millivolt)) {
alpha = a0*exp((v-vha)/vca)
beta = b0*exp((v-vhb)/vcb)
gamma = g0
delta = d0
a = ((Coff/Con)/(Ooff/Oon))^(1/8)
}