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Kv4.mod
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Kv4.mod
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TITLE Voltage-gated potassium channel from Kv4 subunits
COMMENT
NEURON implementation of a potassium channel from Kv4 subunits
Kinetical Scheme: Hodgkin-Huxley m^4*h
Kinetic data taken from: Sacco and Tempia, J.Physiol. 543 (2002) 505
ACTIVATION:
The rate constants of activation (alphan) and deactivation (betan) were approximated by:
alphan = can * exp(-(v+cvan)/ckan)
betan = cbn * exp(-(v+cvbn)/ckbn)
Parameters can, cvan, ckan, cbn, cvbn, ckbn
are defined in the CONSTANT block.
INACTIVATION:
The model includes only the fast component of inactivation
The rate constants of inactivation (alphah) and de-inactivation (betah) were approximated by:
alphah = cah / (1+exp(-(v+cvah)/ckah))
betah = cbh / (1+exp(-(v+cvbh)/ckbh))
Parameters cah, cvah, ckah, cbh, cvbh, ckbh
are defined in the CONSTANT block.
Laboratory for Neuronal Circuit Dynamics
RIKEN Brain Science Institute, Wako City, Japan
http://www.neurodynamics.brain.riken.jp
Reference: Akemann and Knoepfel, J.Neurosci. 26 (2006) 4602
Date of Implementation: April 2005
Contact: akemann@brain.riken.jp
ENDCOMMENT
NEURON {
SUFFIX Kv4
USEION k READ ek WRITE ik
RANGE gk, gbar, ik
GLOBAL ninf, taun, hinf, tauh
}
UNITS {
(mV) = (millivolt)
(mA) = (milliamp)
(nA) = (nanoamp)
(pA) = (picoamp)
(S) = (siemens)
(nS) = (nanosiemens)
(pS) = (picosiemens)
(um) = (micron)
(molar) = (1/liter)
(mM) = (millimolar)
}
CONSTANT {
q10 = 3
can = 0.15743 (1/ms)
cvan = 57 (mV)
ckan = -32.19976 (mV)
cbn = 0.15743 (1/ms)
cvbn = 57 (mV)
ckbn = 37.51346 (mV)
cah = 0.01342 (1/ms)
cvah = 60 (mV)
ckah = -7.86476 (mV)
cbh = 0.04477 (1/ms)
cvbh = 54 (mV)
ckbh = 11.3615 (mV)
}
PARAMETER {
v (mV)
celsius (degC)
gbar = 0.0039 (mho/cm2) <0,1e9>
}
ASSIGNED {
ik (mA/cm2)
ek (mV)
gk (mho/cm2)
qt
ninf
taun (ms)
alphan (1/ms)
betan (1/ms)
hinf
tauh (ms)
alphah (1/ms)
betah (1/ms)
}
STATE { n h }
INITIAL {
qt = q10^((celsius-22 (degC))/10 (degC))
rates(v)
n = ninf
h = hinf
}
BREAKPOINT {
SOLVE states METHOD cnexp
gk = gbar * n^4 * h
ik = gk * (v - ek)
}
DERIVATIVE states {
rates(v)
n' = (ninf-n)/taun
h' = (hinf-h)/tauh
}
PROCEDURE rates(v (mV)) {
alphan = alphanfkt(v)
betan = betanfkt(v)
ninf = alphan / (alphan+betan)
taun = 1 / (qt*(alphan + betan))
alphah = alphahfkt(v)
betah = betahfkt(v)
hinf = alphah / (alphah + betah)
tauh = 1 / (qt*(alphah + betah))
}
FUNCTION alphanfkt(v (mV)) (1/ms) {
alphanfkt = can * exp(-(v+cvan)/ckan)
}
FUNCTION betanfkt(v (mV)) (1/ms) {
betanfkt = cbn * exp(-(v+cvbn)/ckbn)
}
FUNCTION alphahfkt(v (mV)) (1/ms) {
alphahfkt = cah / (1+exp(-(v+cvah)/ckah))
}
FUNCTION betahfkt(v (mV)) (1/ms) {
betahfkt = cbh / (1+exp(-(v+cvbh)/ckbh))
}