TITLE KDR channel
: from Klee Ficker and Heinemann
: modified to account for Dax et al.
: M.Migliore 1997
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
}
PARAMETER {
v (mV)
ek (mV) : must be explicitely def. in hoc
celsius (degC)
gkdrbar=.003 (mho/cm2)
vhalfn=13 (mV)
a0n=0.02 (/ms)
zetan=3 (1)
gmn=0.7 (1)
nmax=2 (1)
q10=1
}
NEURON {
SUFFIX kdrax
USEION k READ ek WRITE ik
RANGE gkdr,gkdrbar
GLOBAL ninf,taun
}
STATE {
n
}
ASSIGNED {
ik (mA/cm2)
ninf
gkdr
taun
}
BREAKPOINT {
SOLVE states METHOD cnexp
gkdr = gkdrbar*n
ik = gkdr*(vek)
}
INITIAL {
rates(v)
n=ninf
}
FUNCTION alpn(v(mV)) {
alpn = exp(1.e3*zetan*(vvhalfn)*9.648e4/(8.315*(273.16+celsius)))
}
FUNCTION betn(v(mV)) {
betn = exp(1.e3*zetan*gmn*(vvhalfn)*9.648e4/(8.315*(273.16+celsius)))
}
DERIVATIVE states { : exact when v held constant; integrates over dt step
rates(v)
n' = (ninf  n)/taun
}
PROCEDURE rates(v (mV)) { :callable from hoc
LOCAL a,qt
qt=q10^((celsius24)/10)
a = alpn(v)
ninf = 1/(1+a)
taun = betn(v)/(qt*a0n*(1+a))
if (taun<nmax) {taun=nmax}
}
