TITLE Q-type calcium current (Cav2.1)
UNITS {
(mV) = (millivolt)
(mA) = (milliamp)
(S) = (siemens)
(molar) = (1/liter)
(mM) = (millimolar)
FARADAY = (faraday) (coulomb)
R = (k-mole) (joule/degC)
}
NEURON {
SUFFIX caq_ms
USEION ca READ cai, cao WRITE ica VALENCE 2
RANGE pbar, ica
}
PARAMETER {
pbar = 0.0 (cm/s)
:q = 1 : room temperature 22 C
q = 3 : body temperature 35 C
}
ASSIGNED {
v (mV)
ica (mA/cm2)
eca (mV)
celsius (degC)
cai (mM)
cao (mM)
minf
mtau (ms)
}
STATE { m }
BREAKPOINT {
SOLVE states METHOD cnexp
ica = pbar*m*m*ghk(v, cai, cao)
}
INITIAL {
rates()
m = minf
}
DERIVATIVE states {
rates()
m' = (minf-m)/mtau*q
}
PROCEDURE rates() {
UNITSOFF
minf = 1/(1+exp((v-(-16.3))/(-7.9)))
mtau = 1.13*2
UNITSON
}
FUNCTION ghk(v (mV), ci (mM), co (mM)) (.001 coul/cm3) {
LOCAL z, eci, eco
z = (1e-3)*2*FARADAY*v/(R*(celsius+273.15))
eco = co*efun(z)
eci = ci*efun(-z)
ghk = (1e-3)*2*FARADAY*(eci-eco)
}
FUNCTION efun(z) {
if (fabs(z) < 1e-4) {
efun = 1-z/2
}else{
efun = z/(exp(z)-1)
}
}
COMMENT
Activation curve was reconstructed for cultured NAc neurons from P5-P32
Charles River rat pups [1]. Activation time constant was measured in
culture neurons from cerebellum of P2-P5 rat pups [2] at room temperature
22 C.
Original NEURON model by Wolf (2005) [3] was modified by Alexander Kozlov
<akozlov@csc.kth.se>. Activation curve was fitted to m2 kinetics [4],
activation time constant was scaled up as well.
[1] Churchill D, Macvicar BA (1998) Biophysical and pharmacological
characterization of voltage-dependent Ca2+ channels in neurons isolated
from rat nucleus accumbens. J Neurophysiol 79(2):635-47.
[2] Randall A, Tsien RW (1995) Pharmacological dissection of multiple
types of Ca2+ channel currents in rat cerebellar granule neurons. J
Neurosci 15(4):2995-3012.
[3] Wolf JA, Moyer JT, Lazarewicz MT, Contreras D, Benoit-Marand M,
O'Donnell P, Finkel LH (2005) NMDA/AMPA ratio impacts state transitions
and entrainment to oscillations in a computational model of the nucleus
accumbens medium spiny projection neuron. J Neurosci 25(40):9080-95.
[4] Brown AM, Schwindt PC, Crill WE (1993) Voltage dependence and
activation kinetics of pharmacologically defined components of the
high-threshold calcium current in rat neocortical neurons. J Neurophysiol
70(4):1530-43.
ENDCOMMENT