TITLE Low threshold calcium current Cerebellum Purkinje Cell Model
COMMENT
Q10 is estimated from this work, Temperature dependence of T-type Calcium channel gating, NEUROSCIENCE
written by Yunliang Zang according to the data provided by Stephane Diudone, compared with the summarised data from stephane,
T type calcium channels has two gates. so the activation curve was refitted.
The junction potential is -6.6 mV
It does not work even changing it back to cai
April 16th, 2015
This version does not contribute to the calcium concentration and BK together with SK.
ENDCOMMENT
INDEPENDENT {t FROM 0 TO 1 WITH 1 (ms)}
NEURON {
SUFFIX CaT3_1
: USEION ca READ cai, cao WRITE ica VALENCE 2
: NONSPECIFIC_CURRENT i
USEION ca READ cai,cao
USEION Ca WRITE iCa VALENCE 2
RANGE g, pcabar, minf, taum, hinf, tauh
RANGE iCa, m ,h
: THREADSAFE
}
UNITS {
(molar) = (1/liter)
(mV) = (millivolt)
(mA) = (milliamp)
(mM) = (millimolar)
}
CONSTANT {
q10 = 1.0913 :estimate from Iftinca
F = 9.6485e4 (coulombs)
R = 8.3145 (joule/kelvin)
}
PARAMETER {
v (mV)
celsius (degC)
eca (mV)
pcabar = 2.5e-4 (cm/s)
cai = 1e-4 (mM) : adjusted for eca=120 mV
cao = 2 (mM)
v0_m_inf = -42.206 (mV)
v0_h_inf = -75.118 (mV)
vshift = -6.6 :liquid junction potential
k_m_inf = -4.7056 (mV)
k_h_inf = 6.4635 (mV)
C_tau_m = 1.2757
A_tau_m = -2.3199
B_tau_m = 2.5712
v0_tau_m1 = -48.048 (mV)
v0_tau_m2 = -28.386 (mV)
k_tau_m1 = 30.655 (mV)
k_tau_m2 = 9.6306 (mV)
C_tau_h = 0.0076
A_tau_h = 0.17746
B_tau_h = 0.13402
v0_tau_h1 = -58.535 (mV)
v0_tau_h2=-101.436
k_tau_h1 = 6.2692 (mV)
k_tau_h2 = -5.5845 (mV)
}
STATE {
m h
}
ASSIGNED {
iCa (mA/cm2)
g (coulombs/cm3)
minf
taum (ms)
hinf
tauh (ms)
qt
T (kelvin)
E (volt)
zeta
}
BREAKPOINT {
SOLVE castate METHOD cnexp
iCa = (1e3) *pcabar*m*m *m*h * g
}
DERIVATIVE castate {
evaluate_fct(v)
m' = (minf - m) / taum
h' = (hinf - h) / tauh
}
FUNCTION ghk2( v (mV), ci (mM), co (mM), z ) (coulombs/cm3) {
E = (1e-3) * v
zeta = (z*F*E)/(R*T)
if ( fabs(1-exp(-zeta)) < 1e-6 ) {
ghk2 = (1e-6) * (z*F) * (ci - co*exp(-zeta)) * (1 + zeta/2)
} else {
ghk2 = (1e-6) * (z*zeta*F) * (ci - co*exp(-zeta)) / (1-exp(-zeta))
}
}
UNITSOFF
INITIAL {
T = kelvinfkt (celsius)
qt = q10^((celsius-32 (degC))/10 (degC))
evaluate_fct(v)
m = minf
h = hinf
}
PROCEDURE evaluate_fct(v(mV)) {
minf = 1.0 / ( 1 + exp((v - v0_m_inf-vshift)/k_m_inf) )^(1/3)
hinf = 1.0 / ( 1 + exp((v - v0_h_inf-vshift)/k_h_inf) )
taum = 1/( C_tau_m + A_tau_m / (1+exp((v0_tau_m1-v-vshift)/ k_tau_m1))+ B_tau_m/ (1+exp((v0_tau_m2-v-vshift)/k_tau_m2)))/qt
tauh = 1/( C_tau_h + A_tau_h / (1+exp((v0_tau_h1-v-vshift)/ k_tau_h1))+ B_tau_h/ (1+exp((v0_tau_h2-v-vshift)/k_tau_h2)))/qt
g = ghk2(v-vshift, cai, cao, 2)
}
FUNCTION kelvinfkt( t (degC) ) (kelvin) {
kelvinfkt = 273.19 + t
}
UNITSON