TITLE l-calcium channel
: l-type calcium channel
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
FARADAY = 96520 (coul)
R = 8.3134 (joule/degC)
KTOMV = .0853 (mV/degC)
}
PARAMETER {
v (mV)
celsius (degC)
gcalbar=.003 (mho/cm2)
ki=.001 (mM)
cai (mM)
cao (mM)
tfa=1
}
NEURON {
SUFFIX cal
USEION ca READ cai,cao WRITE ica
RANGE gcalbar,cai, ica
GLOBAL minf,tau
}
STATE {
m
}
ASSIGNED {
ica (mA/cm2)
gcal (mho/cm2)
minf
tau (ms)
}
INITIAL {
rate(v)
m = minf
}
BREAKPOINT {
SOLVE state METHOD cnexp
gcal = gcalbar*m*m*h2(cai)
ica = gcal*ghk(v,cai,cao)
}
FUNCTION h2(cai(mM)) {
h2 = ki/(ki+cai)
}
FUNCTION ghk(v(mV), ci(mM), co(mM)) (mV) {
LOCAL nu,f
f = KTF(celsius)/2
nu = v/f
ghk=-f*(1. - (ci/co)*exp(nu))*efun(nu)
}
FUNCTION KTF(celsius (DegC)) (mV) {
KTF = ((25./293.15)*(celsius + 273.15))
}
FUNCTION efun(z) {
if (fabs(z) < 1e-4) {
efun = 1 - z/2
}else{
efun = z/(exp(z) - 1)
}
}
FUNCTION alp(v(mV)) (1/ms) {
TABLE FROM -150 TO 150 WITH 200
alp = 15.69*(-1.0*v+81.5)/(exp((-1.0*v+81.5)/10.0)-1.0)
}
FUNCTION bet(v(mV)) (1/ms) {
TABLE FROM -150 TO 150 WITH 200
bet = 0.29*exp(-v/10.86)
}
DERIVATIVE state {
rate(v)
m' = (minf - m)/tau
}
PROCEDURE rate(v (mV)) { :callable from hoc
LOCAL a
a = alp(v)
tau = 1/(tfa*(a + bet(v)))
minf = tfa*a*tau
}