TITLE Thalamocortical neuron T-type calcium channel
COMMENT
T-type calcium channel
Implementation of Meijer et al., 2011
Written by Xu Zhang, UConn, 2018
ENDCOMMENT
NEURON {
SUFFIX tcCaT
USEION ca READ cai, cao WRITE ica
RANGE pca, m_t, minf, taum, h_t, hinf, tauh, cai, pump, ica
}
UNITS {
(molar) = (1/liter)
(mV) = (millivolt)
(mA) = (milliamp)
(mM) = (millimolar)
(um) = (micron)
FARADAY = (faraday) (coulomb)
R = (k-mole) (joule/degC)
}
PARAMETER {
v (mV)
pca = 1e-4 (cm/s)
cao = 2 (mM)
dpt = 1.0 (um)
tau_ca = 5.0 (ms)
kca = 5.1821e-5
}
STATE {
m_t
h_t
}
ASSIGNED {
ica (mA/cm2)
cai (mM)
minf
taum (ms)
hinf
tauh (ms)
}
BREAKPOINT {
SOLVE states METHOD cnexp
ica = pca*(m_t^2)*h_t*ghk(v,cai,cao)
}
DERIVATIVE states {
rates(v)
m_t' = (minf-m_t)/taum
h_t' = (hinf-h_t)/tauh
}
INITIAL {
m_t = 0
h_t = 0
:cai = cabuf
}
PROCEDURE rates(v (mV)) {
minf = 1/(1+exp(-(v+60)/6.2))
taum = 0.204+0.333/(exp(-(v+136)/16.7)+exp((v+19.8)/18.2))
hinf = 1/(1+exp((v+84)/4))
if (v>=-81) {
tauh = 9.33+0.333*exp(-(v+25)/10.5)
} else {
tauh = 0.333*exp((v+470)/66.6)
}
}
FUNCTION ghk(v(mV), ci(mM), co(mM)) (.001 coul/cm3) {
LOCAL z, eci, eco
z = (1e-3)*2*FARADAY*v/(R*(36+273.15))
eco = co*efun(z)
eci = ci*efun(-z)
:high cao charge moves inward
:negative potential charge moves inward
ghk = (.001)*2*FARADAY*(eci - eco)
}
FUNCTION efun(z) {
if (fabs(z) < 1e-4) {
efun = 1 - z/2
}else{
efun = z/(exp(z) - 1)
}
}