COMMENT
Potassium current for the soma
ENDCOMMENT
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
}
NEURON {
SUFFIX Kaxon
USEION k READ ek WRITE ik
RANGE gkaxon, ik
GLOBAL ninf, nexp, ntau
}
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
PARAMETER {
v (mV)
celsius = 24 (degC)
dt (ms)
gkaxon = .0319 (mho/cm2)
ek = 100 (mV)
}
STATE {
n
}
ASSIGNED {
ik (mA/cm2)
ninf
nexp
ntau (ms)
}
INITIAL {
n = ninf
}
BREAKPOINT {
SOLVE states
ik = gkaxon*n*n*n*n*(v  ek)
}
PROCEDURE states() { :exact when v held constant
evaluate_fct(v)
n = n + nexp*(ninf  n)
VERBATIM
return 0;
ENDVERBATIM
}
UNITSOFF
PROCEDURE evaluate_fct(v(mV)) { :Computes rate and other constants at
:current v.
:Call once from HOC to initialize inf at resting v.
LOCAL q10, tinc, alpha, beta
TABLE ninf, nexp, ntau DEPEND dt, celsius FROM 200 TO
100 WITH 300
: q10 = 3^((celsius  24)/10)
q10 = 1 : BPG
tinc = dt*q10
alpha = 0.018*vtrap((v25),25)
beta = 0.0036*vtrap(v35,12)
ntau = 1/(alpha + beta)
ninf = alpha*ntau
nexp = 1Exp(tinc/ntau)
}
FUNCTION vtrap(x,y) { :Traps for 0 in denominator of rate eqns.
if (fabs(x/y) < 1e6) {
vtrap = y*(1  x/y/2)
}else{
vtrap = x/(Exp(x/y)  1)
}
}
FUNCTION Exp(x) {
if (x < 100) {
Exp = 0
}else{
Exp = exp(x)
}
}
UNITSON
