TITLE passive sodium, potassium, calcium, chloride and magnesium channels
COMMENT
Assembled for MyFirstNEURON by Arthur Houweling
ENDCOMMENT
INDEPENDENT { t FROM 0 TO 1 WITH 1 (ms) }
UNITS {
(mV) = (millivolt)
(mA) = (milliamp)
(mM) = (milli/liter)
FARADAY = 96480 (coul)
R = 8.314 (volt-coul/degC)
}
NEURON {
SUFFIX leak
USEION na READ nai,nao WRITE ina
USEION k READ ki,ko WRITE ik
USEION ca READ cai,cao WRITE ica
USEION cl READ cli,clo WRITE icl VALENCE 1
: negative valence not accepted
: if 'ecl' is needed in a MOD-file use '-ecl' instead
USEION mg READ mgi,mgo WRITE img VALENCE 2
RANGE pna,pk,pca,pcl,pmg,ina,ik,ica,icl,img
}
PARAMETER {
v (mV)
celsius (degC)
nai (mM)
nao (mM)
pna= 2.07e-7 (cm/s)
ki (mM)
ko (mM)
pk= 3.45e-6 (cm/s)
cai (mM)
cao (mM)
pca= 0 (cm/s)
cli (mM)
clo (mM)
pcl= 0 (cm/s)
mgi (mM)
mgo (mM)
pmg= 0 (cm/s)
}
ASSIGNED {
ina (mA/cm2)
ik (mA/cm2)
ica (mA/cm2)
icl (mA/cm2)
img (mA/cm2)
}
BREAKPOINT {
ina = pna * ghk(v,nai,nao,1)
ik = pk * ghk(v,ki,ko,1)
ica = pca * ghk(v,cai,cao,2)
icl = pcl * ghk(v,cli,clo,-1)
img = pmg * ghk(v,mgi,mgo,2)
}
FUNCTION ghk( v(mV), ci(mM), co(mM), z) (millicoul/cm3) { LOCAL e, w
w = v * (.001) * z*FARADAY / (R*(celsius+273.16))
if (fabs(w)>1e-4)
{ e = w / (exp(w)-1) }
else
: denominator is small -> Taylor series
{ e = 1-w/2 }
ghk = - (.001) * z*FARADAY * (co-ci*exp(w)) * e
}