TITLE K-A channel from Klee Ficker and Heinemann
: modified to account for Dax A Current ----------
: M.Migliore Jun 1997
: modified by Poirazi on 10/2/00 according to Hoffman_etal97
: to account for I_A distal (>100microns)
: (n) activation, (l) inactivation
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
}
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
PARAMETER {
dt (ms)
v (mV)
ek (mV) : must be explicitely def. in hoc
gkabar=0.018 (mho/cm2)
vhalfn= -1 (mV)
vhalfl=-56 (mV)
}
NEURON {
SUFFIX kad
USEION k READ ek WRITE ik
RANGE gkabar,gka
GLOBAL ninf,linf,taul,taun
}
STATE {
n
l
}
ASSIGNED {
ik (mA/cm2)
ninf
linf
taul
taun
gka
}
INITIAL {
rates(v)
n=ninf
l=linf
gka = gkabar*n^4*l
ik = gka*(v-ek)
}
BREAKPOINT {
SOLVE states
gka = gkabar*n^4*l
ik = gka*(v-ek)
}
FUNCTION alpn(v(mV)) {
alpn = -0.01*(v+34.4)/(exp((v+34.4)/-21)-1)
}
FUNCTION betn(v(mV)) {
betn = 0.01*(v+34.4)/(exp((v+34.4)/21)-1)
}
FUNCTION alpl(v(mV)) {
alpl = -0.01*(v+58)/(exp((v+58)/8.2)-1)
}
FUNCTION betl(v(mV)) {
betl = 0.01*(v+58)/(exp((v+58)/-8.2)-1)
}
LOCAL facn,facl
PROCEDURE states() { : exact when v held constant; integrates over dt step
rates(v)
n = n + facn*(ninf - n)
l = l + facl*(linf - l)
VERBATIM
return 0;
ENDVERBATIM
}
PROCEDURE rates(v (mV)) { :callable from hoc
LOCAL a,b
a = alpn(v)
b = betn(v)
ninf = a/(a + b)
taun = 0.2
facn = (1 - exp(-dt/taun))
a = alpl(v)
b = betl(v)
linf = a/(a + b)
if (v > -20) {
taul = 5 + 2.6*(v+20)/10
} else {
taul = 5
}
facl = (1 - exp(-dt/taul))
}