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Kv3.mod
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Kv3.mod
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TITLE Voltage-gated potassium channel from Kv3 subunits
COMMENT
Voltage-gated potassium channel with high threshold and fast activation/deactivation kinetics
KINETIC SCHEME: Hodgkin-Huxley (n^4)
n'= alpha * (1-n) - betha * n
g(v) = gbar * n^4 * ( v-ek )
The rate constants of activation (alpha) and deactivation (beta) were approximated by:
alpha(v) = ca * exp(-(v+cva)/cka)
beta(v) = cb * exp(-(v+cvb)/ckb)
Parameters can, cvan, ckan, cbn, cvbn, ckbn are given in the CONSTANT block.
Values derive from least-square fits to experimental data of G/Gmax(v) and taun(v) in Martina et al. J Neurophys. 97 (563-671, 2007.
Model includes a calculation of Kv gating current
Reference: Akemann et al., Biophys. J. (2009) 96: 3959-3976
Laboratory for Neuronal Circuit Dynamics
RIKEN Brain Science Institute, Wako City, Japan
http://www.neurodynamics.brain.riken.jp
Date of Implementation: April 2007
Contact: akemann@brain.riken.jp
ENDCOMMENT
NEURON {
SUFFIX Kv3
USEION k READ ek WRITE ik
NONSPECIFIC_CURRENT i
RANGE gbar, g, ik, i, igate, nc
GLOBAL ninf, tau
GLOBAL gateCurrent, gunit
}
UNITS {
(mV) = (millivolt)
(mA) = (milliamp)
(nA) = (nanoamp)
(pA) = (picoamp)
(S) = (siemens)
(mS) = (millisiemens)
(nS) = (nanosiemens)
(pS) = (picosiemens)
(um) = (micron)
(molar) = (1/liter)
(mM) = (millimolar)
}
CONSTANT {
e0 = 1.60217646e-19 (coulombs)
q10 = 2.7
ca = 0.22 (1/ms)
cva = 16 (mV)
cka = -26.5 (mV)
cb = 0.22 (1/ms)
cvb = 16 (mV)
ckb = 26.5 (mV)
zn = 1.9196 (1) : valence of n-gate
}
PARAMETER {
gateCurrent = 0 (1) : gating currents ON = 1 OFF = 0
gbar = 0.005 (S/cm2) <0,1e9>
gunit = 16 (pS) : unitary conductance
}
ASSIGNED {
celsius (degC)
v (mV)
ik (mA/cm2)
igate (mA/cm2)
i (mA/cm2)
ek (mV)
g (S/cm2)
nc (1/cm2)
qt (1)
ninf (1)
tau (ms)
alpha (1/ms)
beta (1/ms)
}
STATE { n }
INITIAL {
nc = (1e12) * gbar / gunit
qt = q10^((celsius-22 (degC))/10 (degC))
rateConst(v)
n = ninf
}
BREAKPOINT {
SOLVE state METHOD cnexp
g = gbar * n^4
ik = g * (v - ek)
igate = nc * (1e6) * e0 * 4 * zn * ngateFlip()
if (gateCurrent != 0) {
i = igate
}
}
DERIVATIVE state {
rateConst(v)
n' = alpha * (1-n) - beta * n
}
PROCEDURE rateConst(v (mV)) {
alpha = qt * alphaFkt(v)
beta = qt * betaFkt(v)
ninf = alpha / (alpha + beta)
tau = 1 / (alpha + beta)
}
FUNCTION alphaFkt(v (mV)) (1/ms) {
alphaFkt = ca * exp(-(v+cva)/cka)
}
FUNCTION betaFkt(v (mV)) (1/ms) {
betaFkt = cb * exp(-(v+cvb)/ckb)
}
FUNCTION ngateFlip() (1/ms) {
ngateFlip = (ninf-n)/tau
}