TITLE Ltype calcium channel with high threshold for activation
: used in somatic and dendritic regions
:
: After Borg
: Updated by Maria Markaki 12/02/03
NEURON {
SUFFIX cal
USEION ca READ cai, eca WRITE ica
RANGE gcalbar, ica, po
GLOBAL inf, s_inf, tau_m
}
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
(molar) = (1/liter)
(mM) = (millimolar)
FARADAY = (faraday) (coulomb)
R = (kmole) (joule/degC)
}
PARAMETER {
ki = 0.025 (mM) : middle point of inactivation fct
gcalbar = 0 (mho/cm2) : initialized conductance
: taumin = 100 (ms) : minimal value of the time cst
taumin = 180 (ms) : minimal value of the time cst
vhalf = 1 (mV) :half potential for activation
zeta=4.6
t0=1.5(ms)
b = 0.01 (mM) :young cell
ba = 0.01 (mM)
bo = 8
}
ASSIGNED { : parameters needed to solve DE
v (mV)
celsius (degC)
cai (mM) : initial internal Ca++ concentration
ica (mA/cm2)
eca (mV)
: ical (mA/cm2)
po
inf
s_inf
tau_m (ms)
}
STATE {
m
s
}
INITIAL {
rates(v,cai)
m = inf : initial activation parameter value
s = s_inf
}
FUNCTION h2(cai(mM)) {
h2 = ki/(ki+cai)
}
BREAKPOINT {
SOLVE states METHOD cnexp
po = m*m*h2(cai)
ica = gcalbar*(po+s*s*bo)*(veca)
}
DERIVATIVE states {
rates(v,cai)
m' = (infm)/t0
s' = (s_infs)/tau_m
}
FUNCTION alp(v(mV)) {
UNITSOFF
alp = exp(1.e3*zeta*(vvhalf)*9.648e4/(8.315*(273.16+celsius)))
UNITSON
}
PROCEDURE rates(v(mV), cai(mM)) {LOCAL a, alpha2
a = alp(v)
inf = 1/(1+a)
alpha2 = (cai/b)^2
s_inf = alpha2 / (alpha2 + 1)
tau_m = taumin+ 1(ms)*1(mM)/(cai+ba)
}
