/
NA12.mod
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NA12.mod
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COMMENT
Model for an SODIUM cuRrent recorded in DA neurons.Nav12 style
Activation and inactivation parameters DERIVED FROM MIGLIORE
ENDCOMMENT
NEURON
{
THREADSAFE
SUFFIX Na12 USEION na READ ena WRITE ina
RANGE gbar, g, i
RANGE atau, btau
RANGE ainf, binf
}
UNITS {
(pS) =(picosiemens)
(mV) = (millivolt)
(mA) = (milliamp)
}
PARAMETER {
gbar = 50 (pS/microm2)
Vmid_ac = -28(mV) : actually corresponds to -20 mV because the m^3 model is rightward shifted
k_ac = 7.7(mV) : corresponds to 7
k_ina = -10 (mV)
Vmid_ina = -50 (mV)
m=3
h=1 : gate parameters according to the HH formalism (m*m*m*h)
celsius = 32 (degC)
q10=1.5
}
ASSIGNED {
v (mV)
ina (mA/cm2)
i (mA/cm2)
g (pS/microm2)
atau (ms)
btau (ms)
ainf (1)
binf (1)
ena (mV)
}
STATE {a b}
BREAKPOINT {
SOLVE states METHOD cnexp
g = (gbar*(a^m)*(b^h))
i = (0.0001)*g*(v-ena)
ina = i
}
INITIAL {
rates(v)
a= ainf
b=binf
}
DERIVATIVE states {
rates(v)
a' = (ainf-a)/atau
b' = (binf-b)/btau
}
FUNCTION a_inf (V (mV)) () {
a_inf = 1/(1+exp(-(V-Vmid_ac)/k_ac)) : activation system (a*a*a)
}
FUNCTION b_inf (V (mV)) () {
b_inf = 1/(1+exp(-(V-Vmid_ina)/k_ina)) : inactivation system (b)
}
FUNCTION a_tau (V (mV)) (ms) {
UNITSOFF
a_tau= 0.01+(0.33/(1+((V+20)/30)^2))
: time constant of activation depends on V
UNITSON
}
FUNCTION b_tau (V (mV)) (ms) {
UNITSOFF
b_tau = 0.7+(16/(1+((V+50)/8)^2))
: fast inactivation
UNITSON
}
PROCEDURE rates(V (mV)) {
LOCAL qt
UNITSOFF
qt=q10^((celsius-24)/10)
UNITSON
atau=a_tau(V)/qt
ainf=a_inf(V)
btau=b_tau(V)/qt
binf=b_inf(V)
}